master cylinder?
i just did this install. but this is a 2 bolt mc
i got a alum m/c off a late 80's 5th ave at the bone yard--it looks new.
fabbed a chunk of 3/8 aluminum for the adapter plate . very easy .
ran 1 new brake line to the prop valve.
i think the whole project cost me around $26.
the brakes work great !