If your car was AM radio equipped it would have a telescopic antenna on the right fron fender or the right rear fender. It should have a chrome, rounded hex nut type affair for a base and a 3-piece telescopic mast. In '66 you could also get a power rear antenna, but I've never seen one up close. If your car came with an AM/FM radio, the mast would not be telescopic. It would be a slender 1-piece affair, 31" in height. Chevy only put the AM/FM antennas in one place - the front fender. Corvettes were the exception.