When I did mine I bought a kit based on mid-70's midsize GM parts. My rear axle came from a '73 Chevelle (wagon) so I bought rotors, calipers and master cylinder for a '73 Chevelle and used the multivalve from the same car.
I had first determined that the Chevelle and my truck weighed close to the same and had similar weight distribution. My thinking was that I was letting the factory engineers figure out details like master cylinder size and proportioning valve.
I'm still driving it eight years later so I think the approach worked.
