Yes, the 489 uses a larger ID but shorter bearing than the 742. Regardless, this is really splitting hairs, as they both use the same smaller front bearing and the front bearing is far more likely to fail.

As far as deflection, perhaps the 742 case is better supported in this area than the 489. I don't know, but if a person is going to sweat the details of this to ensure the strongest rear--get a Dana