Thanks for the very informative response!The antenna for the Caprice is different. It has 4 segments
If you can find an antenna with three mast sections, the motor, and cable can be moved to the Caddy unit. You have to unscrew the finial, and pry the mast base out of the motor unit at the plastic clip in the rubber isolators. I have had occasionally had to heat the finial before trying to unscrew it. You have to hold the mast very firmly in a smooth vice, and use an adjustable wrench on the flats of the finial to get it off. The threads are a 4-40.
You have to transfer the bracket, to the donor motor, and if it has the relay on the mast base, you can just plug the motor wires into it. Make sure the mast is in the same orientation to the motor, or it will not install in the car properly.
You may also be able to get the cable from Amazon.com. The motor and cable from a Roadmaster will also fit. I have used them from any Cadillac, Olds, Buick, Pontiac and Chevy with the same motor unit. Just make sure that the unit works before you leave the junk yard.
You should not have to disassemble the motor unless you are replacing just the cable. If you do, the white gear with the blocking tooth has to be in the correct position to allow the antenna to extend fully.
I have a good used one for $75 and yours in exchange, in case you do not want to do the repair, and just install it.