Various manufacturers tended to do things differently, Peugeot tended to stay all French the longest, as did Gitane, but Motobecane was using British sized stems and threads in the early 70's or earlier. They also tended to use Swiss bottom bracket threads which it nothing more than a reversed fixed cut in bsc thread pitch I believe.
I've given up trying to remember which ones had what, I just measure and make something work while trying to stay as original as the parts supply will allow.