It could be close; I think he's got to be a great driver to equal the 0-60mph and 1/4 mi. times that the car mags got for the GT500...I believe those 'stangs are a bit more difficult to handle than our 335i's. I say with PROcede v2 and your exhaust, you'll take him by at least 2 CLs. It's worth a friendly run if done safely.
btw -- C&D got 4.5 sec. 0-60mph and 12.9 sec. @ 112mph 1/4 mi. for the 500BHP GT500 Cobra...
http://www.caranddriver.com/comparis...lby-gt500.html
Your PROcede v2 335i should be a bit faster than that...like I said above, even if he's a great driver, then you should still beat him by ~ 2 CLs.