the 8 3/4" diff was dropped in virtually all applications in 72 , only the E body continued to 74 so that may be the reason for the cutoff as 72 , either way the flange is the same , it is a simple 5 bolt flange , unbolt the 5 bolt flange slide out the axle , , disconnect the brake line & remove the brake backing plate , the disc system will bolt onto the same flange .