Torsion Bar Replacement

If your car originally had a/c then it most likely had .870 bars from new. Not a bad place to start, and torsion bars can easily changed later if you want something different. Here's how I would proceed:

First make sure the suspension is in good shape and all bushings, joints and linkages are tight and not bent. Sounds like you have a good handle on that.

Next would be a set of high pressure gas shocks. KYBs are a lot of bang for the buck, Bilsteins are a lot more bang for more bucks. KYBs tend to be valved a little stiff, but I've never found them objectionable. Bilsteins are more progressive and all around better.

Then, before you blow any cash on new torsion bars, add a front sway bar. This is the biggest improvement you'll make. Replacing the rears with OEM type HD springs will make a big difference too.

For a street driven car I would stop here. You'll have a smooth riding, nice handling car for not a lot of cash. Later on down the road if you want to take it to the next level, begin with the wheel/tire combo.