Vibration in drive line ?

[RShaips]

I have a 67 SWB that is sitting on a 71 frame. This truck was a total restoration. I am having some vibration that I can feel as I drive it, the faster I go the worse it gets. It has a new driveshaft, that has been balanced and a 700R4 Tranny. It feels like its in my driveline somewhere, I ran it off the ground and everything looks ok. how can I tell if I have a bent axle? Wheels are spinning decent and wheel bearings feel tight. I just put this tranny in, could it be causing this? I don't think its the problem, just can't narrow it down to location, feel it in the seat, mirror vibrates, not in the front end at all. Its a tight fast vibration. Help !