I races with Greg and his bunch with my spec car. They were using Hoisers while I was on Toyo's so they were quicker in corners and, since I was only racing that one weekend, I did not buy tires. My car set up was BAD. Greg did not come up and say that but when I went to him about it, he agreed to haul my car to his shop, work on it and get it to me by that Wednesday so I could drive down to Thunderhill for a race the following weekend. His charges were very reasonable and the car was completely different from then on. I went from a mid pack guy to competing in the front group of cars.
You can build your car to Spec-944 rules, use their tires and do just fine. Greg is the guy to assist you with advice on what you can do and still keep your car spec legal. He is a great driver, as well, and will help you get faster.
Big Dog