Reply to "Vague steering, need help!"

Dago, it may well be your caster, especially with wide tires. Stock Pantera suspension cannot adjust caster to more than about 2.6 degrees back. Corvettes of the same era use up to 6 degrees (with power steering to compensate for the extra steering load, the wimps!) The tiny amount of caster possible produces the car's equivalent of a motorcycle speed-wobble or tank-slapper.
There are a whole variety of ways to increase caster, but the simplest (and completely reversable if you desire) is by adding offset urethane bushings to the upper a-arms. Pantera caster then goes to about -4 degrees. Adding a second set of offset bushings to the lower a-arms increases caster again, to about 5-1/2 degrees total. By shaving 0.080" off one side of the upper ball joint carrier, will give an additional 1/2 degree.
I've found that on a street car, more than about 4-1/2 degrees of caster becomes hard to park or drive slow around town. But 4-1/2 degrees was tolerable and was enough to cure shimmy and hunting in our '72, even on bumpy crowned roads.