I have a similar vibration with my 68 LeBaron. The vibration frequency seems to be proportional to vehicle speed, so its definitely related to the brakes. Phil is suggesting the possibility of wetted drum shoes from past differential leakage. Guess its possible, but my 68 sedan that still has a small leakage on the rear left drum does not have any vibration, but it does have a very slight pull, as expected. My guess is that my problem is related to a warped rotor. It seems to happen after the brakes have been warmed up somewhat. Any suggestions, especially from Budd braked Imp drivers? D^2