A new (reman) MC isn't that expensive, if yours has rust pits. But my solution was to swap to the newer-style ('87-96) MC, reservoir, & booster.
It required a conglomeration of adapters on one of the lines, and I gutted the residual-pressure valve (because I wasn't sure if it would clash with the proportioning valve), but it worked fine for many years.
The '94-96 version (with SCCDS port) makes it easier to swap to the '93-04 cruise servo later. Just be sure to get the black (new, revised) SCCDS instead of the old (flaming) red one.
Making the fluid level switch trigger the original BRAKE light is pretty easy, too. Just splice it into the switch on the proportioning valve, and run a ground: