driveline vibration

got a 95 gts with 5 spd i got a nasty vibe in the drivetrain but not sure where its coming from. it happens aroound 50-70 mph and again at like 90-whatever. im gonna get motor and tranny mounts and a new clutch this weekend .but and info will hepl thanks :flag:
 
ive got bad vibe issues as we speak but mine me may be unrelated to yours,(lowering kit&new tranny combo most likely the culprit) but i would say check your d/s to see if it threw a weight, also check your tires&wheels maybe they threw a weight. check your universals and if your car sat all winter like mine you may have some flat spots in your tires.
 
check your harmonic balancer!!!! it's one of the infamous problems on our cars. They just get plain old worn out. It's a cheap fix to do, and shouldn't take you more than an hour with a couple of hand tools. Check it out, i thought my driveshaft was screwed up, but it wasn't, just a balancer.