8 3/4 Rear End Question

The 489 is stronger but the 741 isn't a weakling like a lot of guys think they are. You could install the sure grip unit from the 489 case into the 741 case with the 3.91 gears. That'd give you the gears and sure grip you want.

BTW: most of the strength difference between a 741 and 489 is the pinion. The 741 pinion is a much smaller o.d. but here's something to think about. What size is the o.d. of the pinion on a 741 right behind the yoke? Answer: it's exactly the same as a 742 or early 489 pinion. Only the newer fine spline 489 gearset is stronger.