Wanting to get some runs at the track where i actually have some traction, so heres the big question...

Will my stock rear end hold up to a ~400hp car thru a spec stage 4 clutch with some 255/50-16 nittos bolted on?

Or are there any other ways to improve my traction without stressing the rear?

 

http://www.lpwracing.com/home.htm

Weld the tubes, get a girlde, solid pinion spacer, maybe a brace kit.. But you won't be wanting to do any 5K Rpm drops or anything.. Probably get by on street tires and a 2k drop with all those parts above..

 

Improving traction will stress your rear end, there's no way around that. Anything you add to your car to help it hook will add stress to an already weak rear. M6 cars are just hard on rears because of the 3000plus rpm clutch drops at the starting line. You can add everything in the hi-po parts book for your rear, BUT there is nothing you can do to make a 7.5" ring gear stronger.

Bolt on the Nittos and be careful. Just start saving for a 12 bolt or a 9". As long as you spin a little your rear end should be ok.
--Alan