Wow, thanks for all the quick responses.

The current calipers are mounted to the rear as factory 73 B's come standard. The caliper is hitting the lower control arm where the banjo bolt connects the rubber line. I have a "stop" I engineered to prevent the arm from crushing the fitting or caliper. My car is a 70 E body and after doing some more research, this interference is common when trying to adapt a B body setup to an E body.

I never thought the boosters would be different and my current one is a little rough so I can start there.

I have bled and re-bled the masters and lines thinking that was my problem but I still have the same issue.