As Steve mentioned, the brake kits use standard car or truck rotors & calipers but the problem is determining which one to use. I used the complete rotors/calipers/hoses from a 74 Malibu on my 56. I purchased a bracket kit from one of the aftermarket suppliers which included the bearings, spacer sleeves, bolts, brackets, etc.
This of course makes it a 5 lug car bolt pattern. The six lug conversion is another whole issue. Some of the kits use your existing hub and a rotor from something like a 73 up 4x4. Most of the aftermarket guys won't share the info about what parts they use as they like to sell kits. There is a lot written on this subject in these forums.
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