I had issues with one set of wheels and tires, I have three different sets , when I mixed bias plys and radials, turn out the wheel lugs( can't think of the proper name for the retainers, lug nuts, on thick center aluminum wheels )where bottoming out on the brake backing plates not keeping the wheels tight against the axles Little stuff can bite the crap out of you My car would go staright as a arrow(128+MPH in the 1/4) with the right set of wheels, not so when I used the wrong rear wheels on it, shortening the wheels retainer shanks up fix it

Sorry to hijack but I'm having the same problems with my 68 GTX. My front end guy said that to keep the camber right left less than a degree of positive caster on each side. Sure doesn't sound like enough.

I put the car one the alignment machine. Its no wonder I have issues

Left Right

Camber -0.9 0.1

Caster 0.9 0.2

Toe 0.28 0.19

What are the idea settings for higher speed stability

Agree as much positive caster as possible and some toe in, about 1/8"-3/16" which should be around stock specs on the high side for stability. For cornering you want a little negative camber. More helps the tires bite in turns. At least -.25 degrees. -.75 camber would help the tires bite even more but you get into a tradeoff with caster.

With stock suspension it can be hard to get enough positive caster. 5 or even 7 degrees of caster would be great. One approach while on the alignment rack is to set both sides for max caster. Even it up between the sides and then set the minimally acceptable negative camber.

Offset UCA bushings or tubular control arms with additional caster built in will help increase both caster and negative camber. See Firm Feel's web site.

Can a torsion bar expert help educate me? Can/does too low of a ride height contribute to poor stability? I had a front end alignment done at a shop on my GTS (all new front end components/bushings/joints), and I'm certain the ride height is too low and the car likes to wander.

Ride height can affect alignment. If this started happening after alignment, maybe you need a better shop.