Aren't Auburns or Auburn Pro non rebuildable? Eatons I believe are. But if you are going to through any hp at it they all suck. Auto's will prolong the inevitable. But being you have a fox and only going to make 350-450 I'd get a 31 spline T-lock. If you want to rebuild your rear one time get either a spool or a locker. But streetability wont' be as good as other diffs. IMO my locker is the best insurance I've bought. -Mark