8 3/4 rear 741 / 742 center case question - HELP!

the 741, 742 and 489 center section can easily be swapped in and out of any 8 3/4 axle housing, a sure grip or locker unit can be swapped between any center section 741, 742, 489, the pinion gear is specific to the center section and will not interchange, a 741 pinion will only fit a 741 section, same for the 724 section and pinion, or the 489,