I looked there earlier but didn't find anything. I suppose a good example of what I'm looking for would be in G where my car is classed at. What technical specifications or perameters allow these cars to run in the same class.
The BMW 318i I-4 RWD, the VW Corrado both V6 and the supercharged I-4 FWD, but with the Scirocco the 16v I-4 is in G and the 8v is in H. The common theme seems to be 2 door, 4 seats, 2 wheel drive, I4 and V6 engines. I assume track, wheelbase and power to weight is also in there as well. Though I'm not finding anything to back that up.