Well, I don't know for sure but I believe they have a sliding wight scale based on mods. You can run a blueprinted motor with header and crank scraper, rear coil overs and any wheel and wheel diameter as long as they are within a certain width. I beleive they run a max 245 DOT tire but you can choose any tire you want, which means Hoosier.
Tires alone would price a lot of us out. Hoosiers do not last long and fall off quicker than out tires plus cost more. Coilovers sound good in theory, ease of adjustment and installation but what shocks do you run? We chose the shocks we have because of cost and they wont work with coilovers in the rear so now you have to find new, more costly ones.
I know a guy who used to run with them and said the top guys spend a LOT! They throw away tires after one weekend! Their motors also cost a ton more than ours.
I think spec cars can run with them midpack and have fun but if you want to win I would guess at least double what you are paying now might get you close.