vibration problem

If it does it while moving, it could in fact be the drive shaft or U joints. Once you eliminate all other possibilites and still have vibration replace your DS with a new FRPP aluminum one. I put one in both my Fox cars years ago and was amazed at how smooth they got.

Good Luck
 
I've also heard that sometimes lowering a car can change pinion angle creating vibration. Trying to sort the same thing out on my car.