WastedDays and myself stripped a 74 Valiant 4 door last summer with a 7 1/4 inch rearend. It had the 10 3/4 inch brakes with flared drums. This was a six cylinder car with Kelsey Hayes disc brakes on the front.
Previous posters are correct in that the backing plates are not compatable with the 8 3/4 rearend.