Driveline vibration help

I'd like to thank those of you that have replied to this thread so far.

67 Dart273 : When I purchased the 8.75 I also bought the shock pads because I was told the 7.25 pads would not fit. The shop that did the installation insists they used the 7.25 pads because the 8.75 pads would not line up. The U joints have been checked and are installed correctly.

GEO : I never drove the car before the rear end was changed so I don't know if the vibration was there before. Axel's and axel and pinion bearings are all new, everything in the reared was replaced before it was installed.

moparlover : I think I'll follow you advice and replace the slip yoke and the U joint once again to see if it corrects the problem. I'll also send the driveshaft out again to be re-balanced. The tail shaft bearing and seal were just replaced about 10 miles ago. Hopefully this will cure it.

MOrePowAR : The driveshaft had to be shortened and the U Joints front and rear were replaced. The driveshaft was sent to Driveshaft Unlimited here in town for the shortening and was also balanced at that time.

To All : Is it possible the tail shaft in the transmission is bent, does that happen? If it is bent wouldn't it be expected to have a vibration at all speeds? Thanks