Get a big hose clamp, and put it on the driveshaft. Clamp a 1-ounce wheel weight on under the clamp screw, and rotate it to different positions around the shaft until you minimize the vibration. Try this on the front, then the rear of the shaft and see if you can make the vibes go away. Don't assume the shaft is balanced; some shops don't do it unless you insist.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!