Disc brake problem need help!

If your asking about the 65-72 Kelsey Hayes, 4 piston caliper, disc brake systems, nothing from the 73 up brakes will interchange.
Two totally different designed brake systems between the 4 piston, and single piston, set up's.
Not even the spindles or the rotors can be used or the backing plate? I would have to start from scratch?
Pat