....the tools to get it apart are pretty standard, a thin wall socket of whatever size
your crank bolts are (14 or 15mm) or the bicycle specific crank bolt wrench version,
and a standard cotterless square tapered crank puller.

I personally would replace the whole thing, but if you do that and go with a single,
you will need a shorter spindle to maintain a decent chainline.

Usually, the length of the BB spindle is specced for a crank by the maker, but
if you buy used and can't find it, you have to kinda eyeball it and experiment some.


Put up a picture of your current crank, if you can, because I'm curious about
what you have that would be swaged and unalterable from this time period.