i think it would be easier to drill out 1 foot on the modern figure and leave one so it could work on both pegs.
you are on the right track thinking a hole saw, but i don't know what a tiny one would be called. inverted drum sander?
depending on the vehicle it might ruin an expensive piece. i know you are probably not planning on selling them, but someday you might.
maybe consult someone with a 3d printer to make a small "stand" with vintage hole on the bottom and modern peg on top. it would be easy enough to fab one up by hand, but if you want a bunch of them might be time consuming.
good luck and let us know how you do it

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The more you run over a dead cat,
the flatter it gets.
-Anonymous