Leaf springs or 4-link for a numbers-matching Firebird? Also: stock A-arms or tubular

[kubcat]

I’m mid-build on my dream 1969 Firebird 400 stroker with a numbers-matching driveline I've owned since 1979. I'm going for an originallooking car to the casual observer, but with key upgrades for performance anddriveability, like the 461 stroker engine and 18x9.5 wheels. Mostly street,maybe some autocross. I care about reversibilityand long-term originality, even though I’ll probably neversell.

The car is still on the rotisserie, and I’m in the process of finalizing suspension decisions.

For the rear, I’m weighing two options:


A RideTech composite leaf spring system — bolt-in, lightweight, reversible
A 4-link setup (RideTech, QA1) for improved traction and adjustability



For the front, I’ve committed to the RideTech TruTurn with tall spindles to fix the steering geometry. The remaining decisions are whether to:


Use tubular A-arms with coilovers, or
Stick with stock A-arms and if so, should I use coilovers of stick with conventional springs/shocks?

➤ Would love to hear your opinions—especially if you’ve driven both leaf and 4-link setups, or compared A-arm options with TruTurn. Here are some pictures for attention:
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[Jk918]

You could go with the ridetech street grip kit for a stock style with better handling or the rear cradle, coilovers on all 4 corners and tubular arms for high level street performance. It all depends on what you want to do with the car and how you want it to feel/drive

[Josh@Ridetech]

If you're going to do the TruTurn, you need to do the tubular arms and coilovers as well. To keep everything in proper geometry (bumpsteer primarily) and be positive that it's going to fit/drive the way we intend it to, I wouldn't recommend using it with stock/coil spring control arms. The only setup that I'm confident installing the TruTurn on is our control arms (I know other people have installed it in other situations but I can't conscientiously give it the stamp of approval :) ).

Personally, I like the four link better as the handling and drivability of the car improve greatly. It's a much more modern type of setup that will give you more room to grow if you want to do more in the future. It's not completely irreversible either. If for whatever reason you wanted to go back to stock, the holes in the frame rails could be welded up and made to look like nothing ever happened.

That being said, the Streetgrip leafs are an easy install and ride fantastic. The only reason I wouldn't recommend it on this car is power level. Once we pass around 400hp, the four link is going to control wheel hop much better than what the leafs will. They're designed more for a cruiser with a good stance.

I just got my '69 going a few months ago so here's a good reference for you (full coilover kit):

217291

[Pedigry]

I run the ridetech 4 link. It works well. It will allow you to run bigger rubber in the rear if you want to down the road. It's a superior system to leafs but more expensive.

[streetk14]

Josh obviously knows the deal. I never had the composite leafs, but I did go from DSE 3” drop leaf springs to the Ridetech 4 link on my ‘68 bird. I’d be worried about wheel hop with that stroker and leaf springs. I had issues with my LS7 putting power down, and I’d guess that Pontiac stroker will make similar torque. The 4 link got rid of my wheel hop and improved the ride quality. Ride height adjustability is an added bonus.

[68Formula]

If you want stealth and reversibility do the front and rear Street Grip with their lower controls arms (they add more caster which you won't get enough with upper or lower stock arms). Then rebuild the uppers with Proforged .5" taller ball joints and Ridetech upper control arm delrin bushings. This way you'll be able to get about 4-5* positive caster (with shimming) and with the hood open, they'll only see stock upper arms and frame.

Or, if you don't mind them seeing tubulars, then run Ridetech's tubular uppers too, which will add even more caster (with less shimming) and already come with the taller balljoint.

[streetk14]

I forgot to mention this, but I did not have any wheel hop with the ~ 425 hp/450 tq Pontiac 400 I had in the car previously. The leafs did not like the jump to 600 hp/550 tq. Something like Caltracs could stop the wheel hop, but that’s probably not the best solution for an all around type of car.