[vanwyk4257]

If you look inside the rear wheelwell in front of the tire you will see a flat metal "plate" and a cylindrical part protruding from it. The part you see protruding is where the outside of the torsion bar inserts into the spring plate. The flat piece that attaches to the rear control arm or "banana" arm as they're sometimes referred to is the spring plate.
I hope that helps.

I would definitely recommend getting a pre-purchase inspection or at a bare minimum having someone who knows these cars well look at them for you. These are great cars, but you can really get in over your head with an early 911/912 if it has major rust problems, and sometimes you won't see them unless you really know what to look for.