how much can the stock rear end take?

 

With these 10 bolts I think traction has a lot to do with how much they will take... Stick cars are harder on the rears than an auto on the launch...To a certain extent, if your tires are spinning, you rear is happy...Put sticky tires on either a high hp stick or an auto and the 10 bolt may have problems...I've been running a 420rwhp 383 for 9 years and only had to replace a failed Auburn with a Pro Auburn...I'm an A4 with BFG DRs, they spin a little and so far no carnage..and I'm running stock axles and GM 3.42s...Moser says you need their axles, a bearing stud kit, and a TA style cover to handle 400rwhp...I think with an M6 it would be a good idea to upgrade to the Moser recommendations or save for a 12 bolt or 9"....
--Alan