Some time ago, I salvaged a set of extremely expensive GMC wheel cylinders by honing the bores about .020" oversize to eliminate pits, and machining new pistons to fit the bigger bore. A standard wheel cylinder rubber cup was able to expand to fit the bigger bore without leaking. Another method is to install a stainless steel sleeve to eliminate the pitted surface. Either way is better than hoping you can order the correct replacement parts. The master cylinder can also be salvaged by installing a sleeve in the bore. It's not a terribly difficult project for any machinist worthy of the name.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!