I'm going to try to post a link to a picture of my 67's antenna. It doesn't look like any I've seen in the catalogs that offer reproductions or NOS. The base of the mast is a ball with a hole through it (diagonally). The ball sits in a pocket (the base that rests on top of the fender) and a screw goes through the ball (diagonally) and into the side of the base pocket.
The threads in the base pocket are stripped on mine. Since the hole isn't deep enough to allow me to re-tap the threads, I figure I probably have to replace the whole unit. I'm not looking for showroom quality reproductions but just something that is relatively simple and looks right for the era.
Augy, I don't think I've ever seen one like it? Not that it would make a difference, or not that I'm any kind of expert... But you should be able to get one of the repro units at a resonable price and replace the whole thing?
I don't know that you'd have much luck in finding parts to fix the one you have, as it seems to be period correct, but maybe not stock equipment?
Augy, You might want to ask Dennie at NOSantennas@aol.com . I was able to buy a correct NOS antenna bezel nut from him for my '68 when all the repro vendors were offering a poor quality one. He advertises in Hemmings. He might know what you have and have a part. Jim