[JLMounce]

The SPM arms allow you to run a LOT of caster because the arm itself is not only reversible, but adjustable without the use of shims. The UMI/BMR/Global West arms are good pieces but all of them use shims for alignment. With the proximity of headers and or exhaust manifolds of a Pontiac engine to the upper control arm mount, this can limit your ability to achieve more caster, which these cars need.

The SPC arms relocate the ball joints at both the upper and lower mount which gives you about 2-3* of positive caster at a neutral alignment setting. In the upper arms forward configuration you can achieve another 4* of positive caster. With the uppers in reverse installation, you can achieve caster rates of around 8* positive. I don't recommend that for a street car because you start seeing some pretty crazy movement of the wheel towards the door of the car, but the option is always there.

My alignment is currently set at just under 6* of positive caster, -1* static camber and 1/16th" toe in. No road crown adjustment.

Since it appears that there are at least some budgetary constraints here, I would recommend the SPC arms and instead of going with the ATS spindle, go with a .9" tall upper ball joint and a .5" tall lower ball joint. Along with the alignment you'll be able to carry with the SPC arms, you'll end up with suspension geometry that is about 90% of a gen 5/6 Camaro. I would go with the SPC springs which are a 1" ride height drop and make sure to get the shim kit for the lower control arms. The SPC lower has a lowered pocket. Without the shims the arms themselves provide about 2" of suspension drop. I'm fairly certain SPC makes a rear coil spring for your car. It's likely a 1" ride height drop as well. If you want to go more in the front, you may need to look for a 2" drop spring for the rear. I'd probably source those from Hotchkis.

Doing this, you retain your current spindle and can continue to use your current brakes. If, in the future you need or want more, you still have the option to move to the ATS spindle and a different front brake package.

As you can see the SPC setup is a little bit more piece meal, but I do believe it's a superior package, especially with a Pontiac engine between the frame rails. If you decide to go with UMI, my suggestion would be to buy their complete setup. Front and rear arms, their springs, sway bars etc.

One thing I want to point out on edit here. Regardless of what system you end up going with here, the cornering and lateral grip capabilities of the car are going to increase by a large enough margin, that if you don't currently have a baffled oil pan in the engine, you will need one.