I've autocrossed my car a couple of times during the fun runs at the end of a school. It was OK, no better. It understeered pretty substantially (which was expected given a tight LS), but was a hoot coming out of the corners.

I've broken the spider gears once on my car and I've got a Powr-Loc in it. One isn't going to sustantially beef up the diff without enough fabrication to install a 9". Having said that, I think that if one stays off the gas over really broken pavement, the rear end should live reasonably well - especially with a stock-ish motor and an AOD.

Peter