[jhv48]

Maybe I'm missing something here.Seems like it would be easy to remove certain systems from the equation.

Am I correct in assuming:

Vibration present revving engine up or down whether car is moving or standing still. (rules out the driveshaft and rear end.)
Vibration present while revving the engine with the clutch in or out while moving or standing still. (Kind of rules out the tranny, maybe not if pilot bushing is really bad, but probably does.)

So, if it were me, I would just remove the trans and then run the motor with the clutch assembly attached. If the vibration is still there, you've eliminated the tranny. Then remove the clutch assembly and then rev the motor. If still there, it's inside the motor. If the vibration is gone, it's the clutch assembly.

My bet is on the clutch.