Earl,
Surprisingly, the links I have worked on so far have been in fairly decent shape. I don't know if they have been worked on or are just hard enough to have minimal wear. Most, if not all, of the link blocks have been replaced. Someone here came up with a fixture that mounts on the milling machine and pivots off the table of an adjacent mill to cut the proper radius on the link blocks when making new ones.
We will eventually have to work on the links. As far as I know the link grinder in Durango is still functional. I am told it is one of the few machines that survived the fire. Another option is to have them machined on a CNC mill. We had the links on 401 done this way at Monticello and it worked very well.
Russ