First off its my 1938 pickup with 59A flathead, 5spd, banjo rear end, open drive shaft and OT front end. Truck was running fine when I parked it but the next time I drove it there was a weird pulsing vibration that started around 50mph. It feels like the front end is going up and down. The vibration starts small and then builds up and then continues to cycle up and down until I slow below 50 mph. I have pulled and visually checked all the tires and then pulled them one at at time replacing them with the spare and it made no difference. Steering seems tight. Disc brakes seem fine. Engine seems to run fine. I have put it in neutral at speed and played with the clutch and no difference. Engine RPM's don't seem to make any difference as it happens at the same 50+ mph in 4th or overdrive. Possibly a bad wheel bearing??? Any suggestions on what to do next would be most welcome.