328hp / 3520lbs * 2640lbs = 248hp.

My 2.4L I4 would have to make 250whp to keep up with it strictly on power to weight.

A 3500lb car with 328whp and the same tires I can fit on my 250whp 2600lb car? It won't run away on the straights, my 2600lb car will be more nimble, and his tires will be toast by the end of a 40 min race. IMO that's very much within the class philosophy on power/weight, and my lighter car will have the advantage in the long run.