Even though it's not all about HP - the stock N/A has about 1 HP for every 14 pounds of vehicle (the SRT is about 1 for 9). Wiki is your friend when sizing up your opponent as it will tell you how much a car weighs and its approximate HP. That'll give you an idea if all factors are the same...but the you need to figure in torque, reaction time, mods, driver skill and so on.