I used a French cottered crank set that I had laying around. I forced on a set of 9/16 pedals into the French threads. I’ve done this several times without problems and it is done by others, but not a common practice. Use whatca got.
Pretty amazed at this to be honest. I did manage to force in some old beefy steel axle Look pedals in old French steel cotter pin cranks (crank arm in the vice, breaker bar on the spanner) but even after it was still a no go for a Shimano pedal. I gave up - I'm too tight arsed to buy imperial pedal taps and the not so local bike shop doesn't bother with this kind of service anymore. It's a shame; there are still many good cranks out there but pedals in a good condition at reasonable prices much less so.