okay just bought this 88 na gxl 7 and when ever i am on the gas at all i mean i touch the gas with my foot i get a nasty vibration its fast and consistent its not wheel related i think it might be the u joints i checked the mounts they look good, the trans mount in the middle(don't know if it is actually a trans mount) the circle piece that the trans actually sits on the trans bracket looks to be shot but not really sure what it is supposed to look like.
the car has an after market exhaust(home made by some jackass) and its close to some things in the rear but i dont think that is it either any ideas

 

and it doesnt vibrate when you just rev it up out of gear so im thinking something drive train

 

it's probably the exhaust I'm guessing. I would have to hear it though.

when you accelerate in gear it puts more load on the engine and it'll vibrate more vibrating the exhaust more too.

 

Well it was 3 thing actually I got it up on a lift a buddy's shop. The u joints were bad the rear caliper was dragging and the exhaust was rubbing on the rear end. Thanks guys