Originally Posted by
randyjawa
Once you have tired clip-less, you will hate going back! I, too, like to preserve the antiquated, or vintage, look. But when it comes to pedals, I automatically fit my clipless mountain bike pedals and away I go. With one exception...
I want to install clip-less on my sixties
Peugeot PX10 but the cranks are 1/2" French thread. I did purchase a new set of 9/16" pedal taps but have not had the courage to use them yet. I certainly have the skill to tap a set of cranks. The problem is, do I want to destroy the original nature of these lovely old 49D cranks?
NO!

j/k
You know, you could tear down the pedals and take the spindles to a machine shop and get them to cut the pedal threads down to 1/2". Possible issue could be the material hardness, the shop should be able to figure out if its doable or not before starting.