1973–1991 K5 Blazer & Jimmy 4×4 Chassis
From 1973 through 1991 the K5 Blazer and GMC Jimmy wore the square-body lines that defined an entire era of GM trucks. It is also the truck Frame-Werx was born from: the chassis was engineered using a 1984 CUCV military K5 Blazer as its template, so every mount, clearance and dimension began with a square-body Blazer on the shop floor.
The result is a chassis that sets a square-body Blazer or Jimmy on modern independent front suspension without disturbing the body, the wheelbase or the stance. Every truck on this page rides on a Frame-Werx chassis today.
Fits
- 1973–1991 Chevrolet K5 Blazer
- 1973–1991 GMC Jimmy
- Choose your model year in the builder so the chassis is built for your truck
Known in the hobby as the square body or 73–91 Blazer.
What is underneath
Independent front suspension
Geometry, steering, hubs and brakes drawn from GM’s GMT900 platform, the same hardware beneath the 2010 Cadillac Escalade, so replacement parts stay easy to find.
Multi-link rear
Locates the axle precisely, so the truck tracks straight at speed and stays composed over broken pavement or a washed-out trail.
Rated to 800 horsepower
Engineered to carry modern GM Performance engine and transmission packages without a second thought.
Two-wheel, four-wheel or all-wheel drive
Configure the drive to suit the truck: two-wheel drive, electronic-shift four-wheel drive or full-time all-wheel drive.
Hot-dip galvanized
Every finished frame is immersed in molten zinc, sealing it against rust inside every rail and crossmember.
Bolts to the factory body
Built to the original body mounting points and proportions. No cutting, no drilling.
Galvanized, not just painted
Once fabrication is finished, every Frame-Werx frame is hot-dip galvanized. The complete structure is submerged in molten zinc, which bonds to the steel inside each rail and crossmember, including the places no spray gun or brush can reach. It is the same protection trusted on bridges and highway guardrail, and it means the foundation of your build will not quietly rust away beneath a fresh coat of paint.
Prefer black? An epoxy primer and flat black finish is also available.
Spec it your way
Choose shocks from a factory-style setup through Fox, King and Rough Country Vertex reservoir coilovers; brakes from a standard aftermarket package to Frame-Werx calipers and Wilwood big-brake kits; a 3.42, 3.73 or 4.10 rear gear; and a GM Performance engine and transmission package. Buy the bare frame, the frame with parts shipped loose, or a complete rolling chassis assembled in Minnesota.
Why we build it
Founder Sean Spraungel on how the Frame-Werx chassis started, why it was built and where it’s headed. Filmed by Classic Truck Performance at Dino’s Git Down 2025.
Watch a K5 Blazer get its new chassis
Factory frame out, Frame-Werx chassis in: a squarebody K5 Blazer rebuilt on a Frame-Werx chassis, in 30 seconds.
Guides for planning your build
Common questions
Will it fit my square-body Blazer without modification?
Yes. It bolts to the factory body mounts with no cutting or drilling. Pick your model year range in the builder (1973–75, 1976–77, 1978–80 or 1981–91) and the chassis is built to fit it.
Can it run a 22-inch wheel package?
Yes. Wheels and tires are part of the builder, and several of the Blazers and Jimmys shown here run large-diameter wheel and tire packages.
Can I buy just the frame?
Yes. The chassis is available as a bare galvanized frame, as a frame with parts shipped loose, or as a complete rolling chassis assembled in our shop.
What does it cost?
A bare hot-dip galvanized frame starts at $17,900. Everything beyond that depends on the parts you choose, and the chassis builder keeps a running total as you go.
How do I order?
Spec your chassis in the builder and review the estimate. Frame-Werx chassis are sold exclusively through K5 Squared, and a deposit reserves your place in the build queue.