I don't have a listing of a source for either the entire rebuilt master cylinder or rebuild kit but the manuals list the diameter as 1-3/4" (compared 1-1/4" for the Ford and Chev 15-60 cwt trucks).
I haven't done an exhaustive (or exhausting) search but
www.steelsoldiers.com www.wheelsofvictory.com www.obschevy.com (Tim Tygart)
www.oldchevytrucks.com (Jimmy Carter)
www.chevsofthe40s.com all came blank so far. I haven't tried catalogue surfing at CarQuest or NAPA yet. Now that I have a C60X I need to start looking for sources for parts to decide about working on it.
Can anyone help with sources?