489 vs. 741

The "weakness" of the 741 case is not the danger of "snapping off" the pinion, as we know all 8.75 pinions use the same diameter spline yoke, it's just the spline count and
u-joint size that varies. If they are going to snap off, that's where it'd happen, and as stated You just don't see that happening on any of the three varieties. The "weakness"
is in the size of the support bearing adjacent to the gear teeth to minimize deflection & keep the teeth engaged at the proper depth. If there is too much deflection the load
moves out towards the edge of the tooth where the strength weakens quickly, and it's an exponential fail as it moves to weaker & weaker contact points as the loads get
higher & higher until You see the teeth stripped of the pinion & part of the ring gear. 'Tis why the 9" Ford is very strong, lots of load support at the gear end of the pinion.
Also this is why proper bearing preload is so important. All this said, an A-body w/a smallblock, even stroked isn't going to fail a 741 case unless something's wrong.