Yah, the old French crank are original to bike. I just the options later in case I put clipless on them so I can ride with my cycling shoes. Might be too costly but I'll keep on the lookout. Looks like VO sells French threaded sealed BB so just thinking of options down the road.
Most later model Nervar cotterless alloy cranks were 9/16" threaded, but I've seen alloy cotterless Nervar cranks in 14x1.25 French thread as well, but most were late 70's issue at best. I've got a 1987 Peugeot with Nervar alloy cranks with 9/16" thread, yet I've got a pair hanging on the wall from a 1980 with French thread. I've also got a set of old Stronglight cranks from the mid 70's off a Motobecane that came through with 9/16" thread. A lot of time it depends on what brand bike they came on.
It shouldn't cost much to have 14 mm pedal threads tapped to 9/16". It takes me less than five minutes. Very little material has to be removed. High speed steel taps cut through aluminum like a hot knife through butter.