No Shortcuts: Inside This Duramax-Swapped Squarebody

AS SEEN IN OUR MAY 2026 ISSUE – Buy Now!

A Squarebody Duramax Swap Done Without Shortcuts

Everybody loves to say they want a squarebody Duramax swap. Very few actually finish one that works like a truck, drives like it should, and doesn’t feel like a science experiment every time you turn the key. This one does.

Owned by Mike Durand and built in-house by DMAXStore, this 1987 Chevrolet R20 is the kind of build that resets expectations and stops you in your tracks. It’s not loud for the sake of being loud. It’s not overbuilt just to prove a point; it exists to show what happens when experience, restraint, and real-world use guide every decision.

Respecting the Squarebody

Squarebodies have always had a way of pulling people in. Simple lines, honest proportions, and just enough edge to remind you trucks weren’t always trying to be comfortable. Mike’s R20 started with that same familiar presence, but the plan was never to preserve it as a time capsule. The goal was to give it modern capability without erasing what made it matter in the first place, and under the hood is where that philosophy becomes obvious.

Modern Power, Proven Platform

The heart of this truck stems from its power plant—a 6.6L LBZ Duramax. Reliable, tunable, and proven under abuse, it was the right choice when Mike’s goal was to build something you can actually trust. The engine is topped with a Garrett stage 1 65 mm turbo, paired with a full WC Fab intake setup including the Y-bridge, intercooler piping, intake, and turbo blanket. Max-Flow components handle heat management and cooling duties, from the manifold blankets to the high-performance water pump and downpipe. DMAXStore performance head studs and a fresh Bosch CP3 pump round out a package that prioritizes longevity just as much as power.

Built to Handle the Torque

Backing the Duramax is an Allison 1000 six-speed transmission built to stage 3 spec by DMAXStore. It’s the obvious choice here, not because it’s trendy, but because it works. It’s smooth when you want it to be, firm when it needs to be, and fully capable of handling the torque this truck puts down without drama, but the drivetrain doesn’t stop at the transmission.

Instead of trying to adapt factory squarebody components past their comfort zone, the decision was made to start fresh with modern heavy-duty axles. Both ends come from a 2006 F-350, with a Dana 60 up front and a Sterling axle in the rear. Matched 4.11 gears and Detroit Truetrac differentials keep power predictable and usable, while Mag Hytec covers add strength and cooling. Custom steel driveshafts tie everything together, and an NP263XHD transfer case handles four-wheel-drive duties without complaint.

Up front, the truck runs a coil spring radius arm setup using Kryptonite Products Ford Death Grip radius arms, custom mounts, and 4.5-inch dual-rate coils. Fox 2.5 Performance Elite DSC shocks keep things controlled whether the truck is cruising highway miles or working off pavement. Out back, Deaver four-inch leaf springs are paired with a one-inch lift block and Pacbrake air bags, giving the truck the ability to handle real weight without sacrificing ride quality. Air management is handled by an Air Lift wireless controller and compressor, with Fox 2.5 Performance Elite shocks completing the rear suspension.

A Stance That Makes Sense

Sitting on 17×9 Battle Born XRAY forged beadlock wheels wrapped in 37-inch Toyo R/T tires, the truck looks ready without feeling cartoonish. It’s the kind of setup that makes sense when you see the whole package together, and in our opinion, it embodies the classic feel with a modern twist that this build aimed for.

Function-First Exterior

Exterior details are clean and functional, with nothing added just for attention. Both front and rear bumpers are custom fabricated, each with integrated winch plates. Baja Designs Squadron Pro fog lights live up front, while the rear bumper houses flush-mount Rigid backup lights and a hitch receiver. Hidden front and rear 12,000-pound winches add serious recovery capability, with the rear winch tucked discreetly behind the license plate.

Lighting continues up top with a Baja Designs linkable XL light bar mounted on custom roof brackets, complemented by LP4 A-pillar lights. Top Gear Autosport headlights modernize the front end without overdoing it, while subtle exterior touches like a blacked-out tailgate bezel, grille, mirrors, and door handles clean up the overall look. The side moldings are gone, leaving the body lines uninterrupted.

Comfort Without Losing Character

Inside the cab, the goal was comfort without losing character. A TMI Products custom bench seat anchors the interior, paired with Guy Designz door panels and kick panels. Sound deadening throughout the cab keeps road noise in check, making long drives far more enjoyable. Entertainment comes from a Pioneer head unit feeding a Morel eight-speaker system and dual 12-inch JL Audio shallow subwoofers. It’s clean, clear, and powerful without being obnoxious.

Modern information is handled through a Dakota Digital Squarebody Syndicate Series gauge cluster, supported by an OBD II CAN interface module. A rearview mirror-mounted backup camera with integrated temperature and compass adds everyday convenience. Amp Research power running boards with frame-mounted brackets make climbing in and out easy without hanging too low.

Built to Tow, Built to Last

Underneath, the truck is just as thoughtfully finished. It sits on a shortened 2006 GM 3500 cab and chassis frame, modified to fit the standard cab long bed perfectly. S&B silicone body mounts isolate vibration, while a custom billet aluminum transmission mount and Max-Flow Arctic transmission cooler ensure durability under load. A custom B&W Turnoverball gooseneck hitch integrates seamlessly with the air bag and shock mounts, reinforcing that this truck was built to tow, not just pose.

Evolution Done Right

This squarebody isn’t about nostalgia for nostalgia’s sake, though; it’s about evolution done right. It proves that you can respect where a truck came from while still pushing it forward in meaningful ways. Every system works together, and nothing feels like an afterthought.

In a world full of half-finished swaps and Instagram builds that never leave the trailer, Mike Durand’s R20 stands as a reminder of what’s possible when experience leads the build. It looks right. It drives right. And most importantly, it still does truck things. That’s the DMAXStore difference.

1987 Chevrolet R20

OWNER : Mike Durand
Gardnerville, NV

BUILDER: DMAXStore

ENGINE & DRIVETRAIN

• 6.6L LBZ Duramax diesel
• Garrett stage 1 65 mm turbo
• WC Fab Y-bridge, intercooler piping, intake, and turbo blanket
• Max-Flow manifold blankets, high-performance water pump, and downpipe
• DMAXStore performance head studs
• Bosch CP3 injection pump
• Allison 1000 six-speed automatic transmission
• Stage 3 DMAXStore-built Allison
• NP263XHD transfer case
• Custom steel driveshafts
• 2006 Ford F-350 Dana 60 front axle
• 4.11 gear ratio
• Detroit Truetrac differential
• Mag Hytec differential cover
• 2006 Ford F-350 Sterling rear axle
• 4.11 gear ratio
• Detroit Truetrac differential
• Mag Hytec differential cover

CHASSIS & SUSPENSION

• 2006 GM 3500 frame
• Coil spring radius arm setup
• Kryptonite Products Ford Death Grip radius arm kit
• Custom crossmember and radius arm mounts
• Kryptonite 4.5-inch dual-rate coil springs
• Fox 2.5 Performance Elite DSC shocks
• Deaver 4-inch leaf springs
• 1-inch lift blocks
• Pacbrake 5,000-pound air bags
• Air Lift wireless controller and single compressor
• Fox 2.5 Performance Elite shocks
• Kryptonite Products drag link, track bar, tie rod, and ball joints
• WFO 3-inch GM HD pitman arm kit and steering box brace
• Custom billet transmission mount
• S&B silicone body mounts
• Max-Flow Arctic transmission cooler
• Custom B&W Turnoverball gooseneck hitch
• Integrated air bag and shock mounts
• Precision Fabrication throttle pedal bracket
• Amp Research power running boards
• Dirt Dynamix umbrella and flag mount

WHEELS & TIRES

• 17×9 Battle Born XRAY forged beadlock wheels
• 37×12.50 Toyo R/T tires

EXTERIOR

• Custom-fabricated front bumper with integrated winch plate
• Baja Designs Squadron Pro fog lights
• Custom fabricated rear bumper with integrated winch plate and hitch receiver
• Rigid flush-mount backup lights
• Front 12,000-pound winch
• Rear 12,000-pound winch hidden behind license plate
• Baja Designs linkable XL roof-mounted light bar with custom brackets
• Baja Designs LP4 A-pillar lights
• Top Gear Autosport headlights
• Blacked-out tailgate bezel, grille, mirrors, and door handles
• Side molding removed

INTERIOR

• TMI Products custom bench seat
• Guy Designz door panels and kick panels
• Pioneer head unit
• Morel eight-speaker audio system
• Dual 12-inch JL Audio shallow subwoofers
• Sound deadening throughout cab
• Dakota Digital Squarebody Syndicate Series gauge cluster
• Dakota Digital OBD II CAN interface module
• Rearview mirror-mounted backup camera with temperature and compass