Driveline Hitting underside of floor (at rear)

unfortunately the problem is the car is too low. (is that possible) these cars would wind up it that situation even when everything was stock due to the springs sagging. they just weren't built with any margin for ride height modification. You my find that the pinion angle is too shallow because of the change in height and find some help in returning it to oem spec. lots of luck in getting where you want to be, My grandfather used to say: "there's more that one way to skin a cat" I think that applies here?