489 vs. 741

You can swap the SG unit from the 741 to the 489 gear/case assembly. Can you set up gears? If not, might be better to sell it, and get the 489 rebuilt with a new SG unit. The early '60s cars, like Max Wedge vehicles only had 741 size pinions. Even the 489 pinion tapers down to the 741 pinion size at the yoke. You can swap to the big yoke on the 741 case, and that's what I'd do.