I really don't think separating protouring cars based on their tire sizes is the right thing to do. Obviously it helps to have more tire, so basically if A guy wants more tire, then it's time to do some mini-tubing and flaring. If you're going to separate the PT cars from the rest of the cars you really can't get too crazy in splitting them up into even more classes, then everything really becomes a mess...
What Jody is trying to get at are the big differences between the vettes, Porsches and Ricers in comparison to the heavy american iron. Traction control, ABS, aero, stability control etc. are all too much for most talented drivers to overcome because of the fact that those cars that finish well not only have all of those aids, but they also are generally lighter and have shorter wheelbases. It doesn't take a rocket scientist to understand that on tight autocrosses and brake stop courses, a little lightweight car is going to have an advantage.
The only time the larger cars have an even playing field would be the road course. Hence why the 5th generation Camaro's and some Pro Touring cars generally do well on the big track with a good driver and good equipment.
How about instead of GT2K, GT3K and AWD you have...
PT, Pro Touring '79 or '89??? and older. Domestics.
AWD, same as before.
GT all other entrants.
By the way, this thread will probably not accomplish much. There are way too many alpha males and type A personalities with bright ideas and big egos to ever come to an agreement on much of anything, but maybe it will spark some type of debate within the Optima group.