Custom Offsets carries suspension, wheels and tires, performance parts, and accessories for the Square Body Chevrolet K20 Suburban. From leveling kits to full lift builds, we have the fitment data and the parts to back it up.
Wheels, tires, and suspension — the complete package for your build. From leveling kits to 12” lifts, paired with the wheels and tires to match. Every setup backed by guaranteed fitment.
See what other owners are running on their 1977 Chevrolet K20 Suburban – real fitment data from real trucks.
No scripts. No call centers. Our team builds and drives the same trucks you do — every recommendation comes from real-world experience. We’re not selling you a part, we’re helping you build your truck.
The third-generation Chevrolet K20 Suburban, built from 1973 through 1986, is one of the most beloved platforms in truck culture. GM called it the Rounded Line generation internally, but the truck community knows it as the Square Body, and that boxy, purposeful silhouette is exactly why builders keep coming back to it. This is a full-size 4WD sport utility built on a proper truck chassis with a leaf-spring rear suspension, a solid front axle, and an 8x6.5 bolt pattern shared with heavy-duty trucks. The engine lineup runs from a 4.1L inline-six up through a 5.7L V8, a 6.6L big-block V8, and a 7.4L V8, with a 6.2L diesel V8 rounding out the options for those who want compression ignition. Shift-on-the-fly 4WD arrived in 1981, adding real-world usability to the platform. Trims ranged from the base work-spec all the way up to the Silverado, which introduced the nameplate that Chevrolet still uses today. The Square Body K20 Suburban is a blank canvas with serious bones, and the aftermarket has never stopped supporting it.
| Spec | Detail |
|---|---|
| Generation | Third Generation (Square Body), 1973-1986 |
| Body Style | Sport Utility (4-door) |
| Drive | 4WD |
| Bolt Pattern | 8x6.5 |
| Hub Bore | 117.00mm |
| OEM Wheel | 16.5x6.00 +10 |
| OEM Tire | 9.50R16.5 |
| Engines | 4.1L I6 (gas/LPG), 4.8L I6, 5.0L V8, 5.7L V8 (gas/LPG), 6.2L V8 Diesel, 6.6L V8, 7.4L V8 |
| Trims | Base, Custom, Custom Deluxe, Deluxe, Scottsdale, Silverado |
The Square Body K20 Suburban left the factory with a slight front-end rake, the nose sitting lower than the rear to account for payload and towing squat. A leveling kit raises the front to eliminate that rake and bring the truck level front-to-rear, giving the Suburban a more aggressive, planted stance right away. At this height the fitment window stays close to stock, but the leveled look transforms the profile of the truck. A 2-inch leveling kit is a strong first move, and it pairs cleanly with a fresh set of shocks to keep the ride sorted after the height change. No major geometry correction needed at this level.
A 3-to-4-inch suspension lift is where the Square Body K20 Suburban starts to look seriously tall. A full lift kit at this height replaces the front and rear components with hardware matched to the new ride height, including longer shocks valved for the added travel. The solid front axle on the K20 makes lift work more straightforward than on independent-front-suspension trucks: there is no CV angle to manage, and geometry correction is simpler. At this height you open up meaningful additional tire clearance, and the truck starts to carry the presence these Square Bodies are known for. Pairing the lift with upgraded steering components is a smart move at this height to keep the front end tight.
Push the Square Body K20 Suburban to a 6-inch or taller lift and you are building a full show-and-go truck. At this height the suspension system is a comprehensive package: new springs, long-travel shocks, and geometry hardware to keep the front axle tracking correctly under the added height. The solid front axle on the K20 is a genuine asset here, handling big lift heights with less drama than independent setups. Taller lifts open the door to the biggest tires the platform can run, and the boxy Square Body silhouette looks exactly right sitting high on a set of aggressive all-terrain or mud-terrain tires. This is the build that turns heads at every show and every cruise night.
The Square Body K20 Suburban's engine lineup spans carbureted inline-sixes and big-block V8s, and the right induction upgrade depends on which engine is under the hood. Carbureted engines from 1973 through the mid-1980s respond well to carburetor upgrades and improved air filtration, freeing up airflow and sharpening throttle response. The 6.2L diesel V8 benefits from improved air filtration as well, supporting better combustion efficiency. On any engine in this lineup, a quality air filter and improved induction path is the easiest first bolt-on, and the results show up in throttle feel and induction sound.
The V8 engines in the Square Body K20 Suburban, from the 5.0L up through the 7.4L big-block, have a natural exhaust note that aftermarket systems bring out properly. A cat-back exhaust replaces everything downstream of the catalytic converter, leaving the cat in place, and on a big-block V8 the result is a deep, authoritative tone that matches the truck's presence. The 6.2L diesel V8 benefits from a turbo-back exhaust that reduces backpressure and frees up flow: the gains here are about breathing and reduced backpressure, not a louder note. Headers are a strong complement to any exhaust upgrade on the V8 engines, improving exhaust scavenging and supporting the rest of the induction work.
The Square Body K20 Suburban's 4WD drivetrain is a legitimate platform for serious mechanical upgrades. Differential rebuilds, ring and pinion gear changes, and axle upgrades are all well-supported for this chassis, and the aftermarket depth here is substantial. For builders running the truck hard off-road or towing regularly, upgraded differential covers protect the gear oil and add a visual element under the truck. Clutch kits, flywheel upgrades, and transmission work round out the drivetrain side for manual-equipped trucks. On the engine side, camshaft upgrades, valve components, and piston and rod work are all available for the V8 engines, making this a platform that rewards builders who want to go deep.
The Square Body K20 Suburban's flat, upright body panels and classic proportions make it one of the most rewarding platforms to build visually: every exterior upgrade reads clearly on this truck, and the interior has plenty of room to work with.
For the show-build Square Body, lighting is where the night presence comes together. LED headlight retrofits are the most impactful single upgrade on this generation: the factory sealed-beam units are functional but dim by modern standards, and a proper LED or projector conversion transforms both the look and the output. Tail light upgrades with LED elements give the rear of the truck a clean, modern contrast against the classic body. For builders running the K20 Suburban off-road or on trail, a bumper-mounted LED light bar throws serious forward light, and ditch lights mounted at the A-pillars cast focused beams to the sides where the factory lights leave gaps. Rock lights mounted under the frame and axles serve the off-road build by illuminating the ground on the trail, and on a show truck they put the suspension and axle hardware on display at night.
The Square Body's flat hood, upright grille, and boxy fenders are a gift for exterior builders. A replacement grille is one of the most visible single changes on this truck, and the aftermarket offers everything from period-correct restorations to aggressive modern interpretations. Hood upgrades, replacement fenders, and door hardware are all well-supported for this generation. For builders running wider tires, fender flares extend the bodyline coverage and protect the paint from the rocks and mud the tires kick up. Front bumper replacements open up options for a cleaner look or a more functional off-road-oriented front end with recovery points. Rocker protection and body armor make sense for trucks that see trail use, keeping the lower body panels intact on rough terrain.
Inside the Square Body K20 Suburban, the priority is protection and comfort. Floor carpet replacements and floor liners are the most practical first move: the factory carpet on a 40-year-old truck has usually seen better days, and a fresh set of liners keeps the new floor protected. Interior trim kits refresh the dash and door panels, and replacement steering wheels give the driver a modern grip without changing the classic character of the cab. Seat accessories and interior storage solutions round out the build for a truck that gets used as a daily or a weekend hauler.
Good: A 2-inch leveling kit with replacement shocks to eliminate the factory rake and level the stance front-to-rear. Better: A 3-to-4-inch full suspension lift with matched shocks and upgraded steering components for a properly tall, capable ride height. Best: A 6-inch or taller full suspension lift with long-travel shocks, geometry hardware, and upgraded front-end components for a show-ready, trail-capable build.
Good: An air filter upgrade and carburetor or induction improvement for the engine in the truck, sharpening throttle response and airflow. Better: A full exhaust system paired with headers and an improved induction setup, bringing out the V8 tone and freeing up the breathing on the whole system. Best: A comprehensive engine build combining induction, exhaust, headers, camshaft, and supporting drivetrain work, with a supporting calibration to get the most out of the combination.
Good: A grille replacement and LED headlight retrofit for an immediate visual update on the classic Square Body face. Better: A front bumper upgrade, fender flares for wider tire coverage, and a light bar or ditch lights for functional forward lighting, plus tail light upgrades. Best: A full exterior package with a custom front end, hood, fenders, rocker protection, body armor for trail use, and a complete lighting suite covering headlights, tails, auxiliary bars, and underbody lighting.
Good: Fresh floor liners and replacement floor carpet to protect and refresh the cabin. Better: Liners, interior trim kit, and a replacement steering wheel for a cleaner, more modern feel inside the classic cab. Best: A full interior refresh with carpet, trim, steering wheel, seat accessories, interior storage, and audio upgrades for a truck that is as dialed inside as it is outside.
Good: 15x7 +13 with 235/75R15 all-terrain tires on stock suspension, a period-correct fitment that mirrors the factory Base and Custom Deluxe spec and bolts on clean. Better: 16x8 +10 with 265/75R16 all-terrain tires on a 2-to-3-inch leveling kit, a wider, more aggressive stance that fits cleanly with the leveled height. Best: 17x8.5 -12 with 35x12.50R17 mud-terrain tires on a 6-inch lift, a bold, aggressive fitment that uses the full clearance the lift opens up and will need minor trimming to run clean.
Good: A clean, honest Square Body restoration with a leveled stance and refreshed mechanicals, a truck that looks right and drives right. Better: An aggressive, capable build with real lift, real presence, and the performance to back it up on the street or the trail. Best: A full show-and-go Square Body built to be seen, with maximum visual presence, a serious powertrain, and the kind of stance that stops people in the parking lot.
It depends on your goal. Builders chasing stance and presence usually start with suspension, getting the truck to the right height before choosing wheels and tires to match. Builders focused on the look first often start with wheels and tires and add lift later. Performance-first builders start under the hood. There is no wrong entry point: pick the category that matters most to your build and work outward from there. Our team can help you map a sequence that makes sense for your specific truck.
Yes. Get pre-approved before you build your cart so you know your budget going in. Pre-approval is fast and does not require a completed order. Once you know what you are working with, you can put together the full build without guessing. Financing options are available at checkout, but starting with pre-approval means you shop with confidence instead of surprises at the end.
Absolutely. The Square Body K20 Suburban has a solid front axle and an 8x6.5 bolt pattern, and our team knows the fitment nuances of this platform well. We can walk you through clearance questions, offset selection for a specific lift height, and install-side questions like what hardware you need and what to watch for during the build. Call or reach out and we will get you the right answers for your specific truck and setup.
We are a truck-first brand with real fitment data behind every recommendation. The Square Body K20 Suburban is a platform our community builds seriously, and we carry the suspension, performance, and exterior parts to support it from a leveling kit all the way to a full show build. Every recommendation is backed by real fitment knowledge, not a generic catalog lookup. We stand behind the fit and the build, not just the sale.
