I can't say I've heard of a standard thread marking actually stating 14 mm. 99.9% the English 9/16x20 is the thread you have. Not everything on a '70s UO-8 was French or metric. Peug were building a highly mass-produced bicycle, and in that business you have to spec out parts that you can get a lot of. The whole rest of the world was already mainly using the British thread.

Another point is that your Sugino crank is not the original, if it was a 1975 bike. Mine is possibly 1971 thru 1975 according to Miami Jim's site on Peugs, and it came with a very rusty steel cottered crank. My extremely clear recollection of these bikes, and the catalog pics, is that this is actually the original equipment. Someone along the way did a cottered to Sugino cotterless upgrade on your bike.

Now after up to 34 years you think that Sugino is at the end of its life, but that's not all so clear from what you've said, "they're shot." What's actually wrong with the cranks? About all that can happen to the crank arms is cracking or breakage. A swaged spider (swaged to the right crank arm) may be coming loose from the crank arm, as well. A crunchiness while spinning is a bottom bracket problem, and chainwheel or tooth problems can be cured by replacing the chainring. Be careful with those pedal threads, you will need them intact if you decide to keep using the Sugino.

Tell us more, it doesn't sound like you've described the real problem.

Re the thread, take a very finely-graduated scale and carefully measure across the group of thread peaks, and accurately count the number of threads. Do some simple arithmetic with a calculator to find the number of threads per inch. You should come up with something between 18 and 22. If you do, I really think you have, as we said, English 9/16 x 20.

I wouldn't make too much of the First of Taichung identification. Get a good measurement of what you have instead.

Regarding period correct, your Lyotard pedals are probably as correct as anything can be. I recall rattrap-style pedals on those bikes, and the catalogs agree.