Or you could make a metal bracket to go from under the rear bumper brace ( bracket mounts to frame) up the side of the rear fender and mount the antenna on it and no holes in a new stang. Paint to match car color.
It works on Pick up trucks and car owners that do not wish to punch holes in their car. Simple, cheap. and can be moved to another vehicle in case you wish to buy a Chevy.
I cringe just thinking of drilling holes a Stang.
By the way. Why does the antenna have to be on the rear?. Tradition? You could put on a trunk lip mount on the hood and you don't open the hood often but you do have a lot more clearance and the antenna just might not hit the roof . just a suggestion or two.
Best of luck. No holes is best.
Every hole is a beginning place for rust to start.
for me. Drilling a hole is last resort with no other options left.
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They don't care,
but they know.