I find the results of your race completely plausible. A 2001 Trans Am weighs 3,500 pounds. The Crossfire 3,060. 440 pounds difference.

A Crossfire with 268 horsepower has a pound/horsepower ratio of 11.5.

A Trans Am with 310 horsepower has a pound/horsepower ration of 11.3.

The difference is neglible and so were the results of the race.

Remember, a Lotus Elise (2,000 lbs) with 190hp can beat a stock SRT-6 to 60mph.