An adjustable frame jig is definitely the way to go. If I’d known I was going to have to do this much work I might have built one. Then again, if I’d known that, I would probably bought a different car. too late now. Some pictures attached of how I did it. My car had mostly old rust repair damage, poorly done. Interestingly enough, the distance between the passenger side spring perches was 3/16” short - from the factory. When I replaced the part of the driver’s side sub-frame I built it to factory spec. I plan to shim the passenger side rear spring hangar to make up the difference when I’m done. It was probably just luck, but when I got everything back together it was still straight and square, and met the specs on the factory frame chart. Thanks again for your advice.