You might be able to install a complete brake system from something like a P-30 motorhome chassis, all the way to the disc/drum assemblies at the front and rear hubs, but mixing and matching old and new components without a degree in automotive engineering isn't a good thing, in my decidedly biased opinion. The older rigs with the Hydrovac ran untold millions of miles relatively disaster-free, so it's not like there was a lack of design ability and experience at building a safe brake system back then. Get the brake system in as close to brand new condition as possible and drive it safely. A C-60 is a big truck, designed to haul heavy loads on a daily basis. Running unloaded, the rear wheels have a definite tendency to lock up and slide. Do you intend to use it as it was designed, or as some kind of oversized Cowboy Cadillac that never sees anything resembling a full gross weight load?
Jerry