Not completely true.....they will all bolt into the housing but there are some interchange problems. If you're swapping between a sure grip and non-sure grip, the axle lengths are different by about an 1/8 of an inch. It's fairly easy to lop off an 1/8 but adding it on is more of a problem. If it's an early housing the end play has to be set with shims which are a pain also. If it's the later flanged type axle shaft, it's just a matter of turning the adjuster on the RH bearing retainer but there is not enough adjustment to make up 1/4" on either type. The 741, 742, and 489 used just about the same thickness center spacer on all their applications so those carriers are not an issue.....just the earlier ones.
