body twist and subframes

I have a 318 4 barrel in a 73 duster. The motor is a dog, and the car has no sub frame connectors. The doors close perfect and the body lines seem to match up. when the car is put into drive the driver side front feels like it lifts a little. when I stomp the gas it really feels like its pulling up. under slow acceleration it does not do it that much. when the car is put into reverse it seems to do the opposite just note as bad. I searched the forums and didn't find what i was looking for. I under stand body twist. I am going to use the mopar performance bolt in connecters and weld them in. I know this will probally take care of most of the lift feeling issues caused by twisting. the front end seems to be sitting level when the car is off. the back end seems the passenger side is a little higher. The guy who i got the car from put B body shocks in the rear so he says. car has the little rear end if that makes a diffrance. there is no cracking in the paint near windows or anywhere else I can see ok my qestions are
1. could the rear springs be what is causing the lean, do springs wear out like that. Dosnt the passenger side tire lift under accelration?
2. after thirty plus years will/could the uni body be trashed.
3. when in reverse and brakes on the rear seems to level out a little. should i bolt the sub frames on with the car in reverse holding the brakes and then drive it real gentle or tow it to where im getting them welded.
4. or should i shim the rear end on one side to level it out. is that dumb, dangerous or wont do a damn thing?
5. could the lifting be a worn out front end.
Im gonna build a mild 360 or 383, that will see street strip use. i want the car to launch strait and i dont want the problem to hurt the car furthure so im doing sub frames before anything else. and want to get it right.

thanks guys