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I've done it to my '72 and '73. It was quite a while ago, but I think all of the major parts suppliers have the kits (I think I got mine from Ecklers).
I got a generic power antenna from Amazon. Nothing stock about my car so no big deal. Made a brackets to mount the bottom. Has worked every time and reception is good.
Essentially a mounting bracket and a relay. The AIMs for the years the power antenna was available show installation diagrams and will give you an idea of the bracket.
From: Graceland in a Not Correctly Restored Stingray
FWIW, I have a NOS aftermarket kit somewhere among my "collection" that I'll sell for 50% of MSRP plus shipping (PayPal accepted). PM with a zip code if interested, and I'll find it and make sure it's all there.