1971 Duster Handeling

what's the rear tire size and rim size?

sounds like front end is catching a bunch of air and raising car in front those speeds

again do you have stock size front torsion bars?
Egzactly. As you know when one looks at real road race cars, they all had their bodies as low as possible.
Same rake can help, but if air is getting underneath, thats a problem.
If the suspension has been raised, that's going to hurt geometries for stability as well as roll center heights.