[sweet70beast]

79 and 80 Firebird is my guess if it's 5x4.75. My Nova has this same set up on it from a 79 Caddy. The Firebird and the Caddy disc setup is the same except the Caddy is 5x5 plus the Caddy is coil sprung. Everything between the two seems to be the same, even the rotors except they are drilled the Caddy with the bigger pattern.
I have Caddy backing plates, calipers, master cylinder and prop valve from the Caddy and rotors from the Firebird. This is on my stock 8.5 Nova rear, everything bolted right on.