Disc brakes are a good upgrade but it depends on how and where you plan to drive the truck. No, the stock master will not work. 4 wheel discs are not necessary unless you plan to have 500 HP.
I always use a dual diaphram booster with a dual master cylinder and a proportioning valve on the conversions I do. Expect to pay around $600 to $800 for the conversion parts.
Fred

1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine