OEM Street Class
Building the combination in your head is the best part, and its free! it goes downhill after that.
Its always more expensive per second of ET to build a car to rules than it is to just build it the way you want.
For example, think about how much it costs for a *good* set of big block heads. I guarantee you'll have more money in porting, valve job, springs, etc. on a set of junky stock heads to race that class, and your car will be slower than if you had just bought the good heads in the first place.