Swapping an A-body 12-bolt into a G-body sounds simple on paper—until you’re under the car wondering why the suspension binds, the pinion angle is weird, and the car feels “almost” right but never truly happy. That’s exactly where my El Camino started: it worked, but nowhere near as well as it should have.
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Trick Chassis Swap Kit: 12 bolt swap kit
“Close Enough” 12-Bolt Swap Problems
When I first slid the A-body 12-bolt under my G-body El Camino, I got it “close enough” to make passes. It went down the track, but:
- The rear suspension would bind mid-travel
- Pinion angle was hard to get where it needed to be
- The geometry wasn’t putting the instant center where I wanted it
On paper, the car hooked. In reality, it was inconsistent and leaving ET on the table.
A big part of the problem came from mismatched parts. I discovered the lower control arms on the car were too short, artificially pulling the pinion up and limiting how much angle I could dial in. Later, I made the opposite mistake: I ended up with lower arms that were about 2 inches too long—they were actually B-body length, not G-body. That pushed the pinion into “U-joint breaking” territory when I cycled the suspension.
Lesson one: verify control arm length for your platform before bolting anything in, especially when mixing A-body, G-body, and B-body parts.
Fixing It with Proper Brackets and Geometry
To get things truly right, I went to a full set of chassis brackets and adjustable arms designed specifically for this combination. That let me:
- Install bearing-style upper mounts in the 12-bolt ears
- Weld in reinforced upper control arm frame brackets in the correct location
- Use adjustable upper and lower arms to set both instant center and pinion angle where I wanted them
Once everything was mocked up, I:
- Squared the rearend in the car using a tape measure from a common point up front
- Set the car at ride height and adjusted pinion angle to about 1–3° nose-down to account for rotation on launch
- Used an instant center calculator to target an instant center roughly forward and near the car’s center of mass, then moved the upper and lower mounts to hit that zone
I ended up with the lower arms nearly parallel to the ground and the uppers moved to give a strong but not insane antisquat—enough separation to hit the tire hard, without being violent or inconsistent.
Don’t Forget the Details
A few extra lessons that matter more than people admit:
- Torque everything at ride height. That’s where a good torque wrench earns its keep and prevents bushing preload.
- The G-body torque box metal is flimsy. Once I had everything welded, I understood why frame-to-torque-box braces exist—bracing that area is a smart “next step.”
- Take your time on the first bolt. After that, replace one arm or bracket at a time so you don’t completely lose your reference.
What This Swap Taught Me
Doing the A-body 12-bolt swap “good enough” got the car moving. Doing it right with proper brackets, correct-length arms, and intentional instant center placement made the rear suspension smooth, predictable, and far more efficient.
If you’re planning a 12-bolt swap into a G-body:
- Make sure you order G-body length control arms
- Plan for proper upper brackets instead of hacking stock mounts to fit
- Use an instant center calculator and aim for geometry—not guesswork
Get the hard points right the first time, and your car will be easier to tune, quicker on the track, and a lot more fun to drive.
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