You got rotors that need to be re-drilled. Not off shelf. Does the rotor need a rotor adapter (ring) between the rotor and hub? or is that just with 73-76 Drum spindles?
Not a fan of that stamped steel caliper adapter. They have put welded in nuts to hold the floating caliper bolt now. Welding can warp the nuts.
I don't doubt it works for people. Just if you are trying to go 5 on 4.5 I think the stock stuff just is a stouter more bulletproof system.