1971 Chevelle Convertible brake conversion help

[ford77id]

I'm helping a friend convert his front brakes from drum to disk. He has the rotors, calipers, caliper brackets, etc. In essence everything to change on the spindles. What I'm wondering is if he also needs a new master cylinder and proportioning valve? Any help would be appreciated. Thanks.

[maxwedge]

Definelty, the m/c for disc/ drum must be sourced and a prop valve.