2002 Camaro SS: 3500lbs & 325hp; 10.77 Lbs/hp
2003 Mustang Cobra: 3665 & 390hp; 9.40 Lbs/hp
2010 GT500: 3900lbs & 540hp; 7.22 Lbs/hp
2010 Camaro SS: 3900lbs & 426hp; 9.15 Lbs/hp
So in this simple comparison, the new cars SHOULD be faster than their previous counterparts. Also, the SS should be a damn good race with a stock cobra with equal drivers. We'll see.
2008 Nissan GT-R: 3830Lbs & 478hp: 8.01 Lbs/hp. New GT500 should take it if its not from a dead stop.