[dsraven]

stock solid axle?
want to keep the same wheel bolt pattern as the rear?
gonna use a proportioning valve from a different vehicle with roughly the same set up or go with an adjustable proportioning valve?
you should know if you want power or manual brakes before you buy the new master cylinder because the bore diameter of the master cylinder can be a different size for the two and a larger bore with manual brakes equals more pedal/leg effort to get the same amount of braking. a smaller bore is easier to push but displaces less fluid so the pedal travels further down to get the same amount of fluid displaced. ensure the rear brakes are adjusted properly and have a park brake set that works and is also adjusted properly (loosened off before the service brakes are adjusted, then adjusted when the service brake adjustment is completed). you will need a new master brake cylinder because the stock one is a single system, meaning it only has one circuit in it to operate front and rear brakes. if you lose one of those systems due to leak or whatever then you lose both front and rear brakes at the same time. newer systems, since the '60's, have dual circuits. you will also need to know which circuit is sup[posed to connect to which port on the new master cylinder.
check
all brake steel lines and rubber lines for dents, corrosion or mechanical damage.
wheel cylinders for leakage
rear brake linings for wear
park brake components for wear and service
adjust rear brakes then park brakes
all brake linkages for wear/mechanical damages/binding from the pedal down to the master cylinder