Need a good car for gt all stars

[The_real_stig]

Im trying to find a good car to compete in the gt all stars championship. Here are the best cars I have: dodge viper srt 10 acr, lamborghini murcielago lp670-4 sv, Nissan gtr '07, corvette zr1 (c6), Ferrari 458 italia, bugatti veyron 16.4(09), and a mclaren f1 stealth model (modded to the max). I tried the gt all stars with the mclaren, and got beat real bad. Now, I'm pretty damn good at gt, been playing since gt1. My question is: do I mod one of these cars, or just buy a proper race car. I figure if I can't hang in the mclaren, I should either mod the veyron, or just buy a proper race car. Any suggestions would be most appreciated.