52 T,
I would bite the bullet and buy new ones. My 46 cables were in the same shape.
I figured that even if I got them moving again, they would not work right. From my bicycle days, good cables are the recipe for smooth working controls. On bikes, we always dumped old cables...
You can get the plastic coated ones for a reasonable price. If you are going to go resto-correct, the steel wrapped ones are going to cost you.
You can try E-bay..it is hit or miss on NOS stuff.
