Need Advice, Suggestions

Wow....Yes the 5 leaf spring goes on the pass. side. Pinion angle is more then likely the main issue. I have to believe those perches were welded on off the car (guessing to be close) and not mocked up on your car for a close angle. In my opinion that's too far off to shim and will likely need them cut off and installed in the proper place. I think you should talk to Gary about replacing that shaft with a modern one piece while your doing this. I can't speak to a direct replacement from another car because i'm not real familiar with the early A body's. Someone here will surely know if and what other model shafts would work.