If the rears are rubbing on the inner top there usually are rub marks. You could pound out there some and remove any undercoating.

But you probably can get more clearance if you add some spacers and move the wheel outward a little. But to do that you need room between outside of the tire to the lip. That's why I posted the rear lipping how to pics.

Does the car still have the hotchkis lowered front Spring hangers? If so, you can put the stock hangers back on and lift the body about an inch in the rear. That will change pinion angle.