Stock D/S.
I use to think that axle shafts would be the 1st thing to go, but that was before I saw DALE ROYSTER's car and what it does at the track and how hard he launches it with the stock 8.8 28 spline axle shafts. He leaves the line at 5,000 rpm's with M/T ET Streets and hasn't had a problem with the rear end. YET! I'm not saying it's going to last FOREVER, but it's held up so far. Not sure how many passes he has, but I saw him run 12.1's and 12.2's @ 114 all last weekend.
BTW 31 splines (or more) to answer your ? FallenPhoenix.