All the c5 vette diff upgrades are just polished stock stuff that anyone can distroy with high power levels. The only proven upgrade so far is switching the c5 diff over to a c6z or zr1 diff. You need the rear subframe also. It's approx 1" larger ring gear and has better attachment to the subframe.
I have a some upgrades in mine with 3.90's, but wheelhop can kill any IRS built or not.