For mor info, the FB page Corvair Owners Group has lots of good people to answer, but I can think of 5 things off the top of my head. Bent wheel, bad bearings, or bad u-joint, out-of-balance brake drums, bad pitman or idle bushing.
The bent wheel might be seen by a pedestrian while you drive, or raise the wheel and turn it with a fixed object next to it. They can be straightened, as I did on my Dauphine.
I have a vibration on my 88 BMW 325ic that can only be corrected with the high speed balancing on the car, and its been a few years since I found anyone who still had that equipment (that I could never use on the rear because of the limited slip differential and rear wheels that don't fin on the front.