Did you look at the link cv129 posted? That's the upgraded diff. The stock Nismo LSD is no different than your sport LSD.
Probably no on the diff brace. I believe that exhaust has axle-back style canisters. It's possible but you'll need to do some research to find out. You might not even find out and will have to be the guinea pig if you want to try it out.
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2011 370Z 6MT Sport Gun Metallic | ARC | CJM | Ecutek | FI | Fujimura | R2C | SPL | Stillen | TWM | Z1 | ZSpeed | |