The diameter of the different seals at the yoke are all the same. The difference is which case you have. 741,489 use a NAPA 18708. While the 742 uses 18912.
Well the 741 and 489 use the same bearing race on the small end, M88048. I never checked but the large bearing races may be the same outside diameter? I don't know I'll have to check.This has nothing to do with the original question but I have seen many original 489 cases with a 7260 yoke. 10 and 29 spline alike. I have seen more 741 cases with a 7290 yoke than 489's or 742's.
Apparently there is a way to use 741 gears in a 489 case because I once bought a 489 not knowing it had 741 gears in it. Wish I would have written down the bearings and races used but I didn't
7260 is the smallest yoke of all three yokes available, but you can put that on all three pinion/housing as long as they are the same spline count Aka coarse or fine spline.I have a 742 case in my convertible with the 7260 u joint!!