People have enlarged the hole to fit the rear nut but as you found already, you won't get much encouragement to replace anything but your old brake shoes on those Mafac Racers. My first "nice" bike was a U-O8 and I tinkered with cranks and derailleurs, but never the Racers😉
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I don't do: disks, tubeless, e-shifting, or bead head nymphs. But I do hate all e-bikes.