bottoming out

Just Suspension is selling their 1" A-body torsion bars for $199 right now. I've seen them on sale as low at $159, but I'm not sure you'll see them offer that price again.

If the car was originally a /6, then you can bet it probably has those tiny /6 torsion bars in it, and that's probably a lot of your problem. But, if the bushings have never been replaced you should do that when you install the new torsion bars as well.