"plan B" might be to use the original style antenna for looks, or skip it altogether, and install a modern electronic one for function ... they are usually recommended to be stuck to a glass panel [windshield!] so they are a small distance away from metal, under the dash doesn't work well under any circumstances - I figured a way to do it for a buddy who didn't want to drill a hole in his pristine fender, so it's
not noticed [inset shows it]
Bill