Finally, have the driveshaft balanced when you are finished. All speed shops will be able to send it out to get done. But be careful! My speed shop quoted me a price of $240!!!!!!!!!! I asked around at a few scattered speed shops in my area and found a shop who charged $65 for the balance. Also be sure the 2 halves are put back in the correct position, also called phasing order . Then be sure the shop balances both halves together. Some shops I spoke with balance the halves separately. I believe that balancing the halves together is the best way. Buick originally balanced the driveshaft with the rear pinion yoke attached. Which is why you should mark the yoke on the end of the driveshaft and the yoke on the pinion. The 2 parts should go back facing the way they were originally. I just hit the edge of the yokes with a shot of silver paint. That way I know which way to bolt them back together.