I just bought a 51 GMC 3 ton that needs a master cylinder. If there's a possibility your old one might be compatible to that application I have the machining facilities and experience to put a stainless steel sleeve into it. Maybe we could do a little trading by PM?
Jerry
Jerry if the 53 Chevy 6400 2 ton MC is the same and you need a decent rebuildable core let me know. Just know I did exchange the end cap from my new one to my old one. I'm not sure how bad the bore is, it may just need cleaned up & honed. This MC is singe chamber with 1.25 bore.
Dan