Originally Posted by
Kovkov
Keep the cottered crank. Just install the new pins properly with a cotter press and you‘ll never have any trouble removing them again.
+ 1. This is the most straightforward solution.
It may be possible to run a cotterless spindle using the existing cups. That requires some trial and error but I did that to a 70s era Peugeot UE 8; so far it's working just fine.