i would just upgrade to aluminum or 3.3 diff cases for the diffs, and only on stock motors i would not worry about breaking the diffs. also the bulks are ususally the first thing to break so you might want to pick up some gray 3.3 bulkheads and those are cheap.
Just finished replacing my black bulks with gray ones. They are definately reinforced. Should be stronger.
my 2 cents: I used 3.3 shafts to the wheels w/ RPM arms and knuckles. I puchased dogbone centers from RC-monster. A brushless setup may spin the pins out of the CVDs then you have more repairs again.