Hmmm...I'm kinda new to this advice thing, but you may have either a bad motormount(s) or you may have bent the driveshaft. I wont say anymore cause I dont want to give bad advice, so I'll just wait to see if others agree
------------------
Blueneonman - '95 5.0L Mustang GT Convertible | K&N Drop-in | FMS 9mm Wires | Hi-Flow Cats | Flowmaster 2 Chambers | Subframes | 6-pt Rollcage | 14deg Timing | Coolest Neon Lighting on a Mustang EVER!