Nick,

Run the 741. It uses a smaller bearing at the pinion head, but not by much, and it's not likely to fail.
It also has the significant advantage over the 489 of not using the crush sleeve (they suck).

As always, set up is important, you want a healthy differential section (preferably good aftermarket or a power lock clutch type) and a ring and pinion that is not showing abnormal wear. As far as strengthening, the first area to look at would be the main caps (carrier) but you are very likely fine with stock.