We are currently refining the TA2 class rules to be pretty much essentially what you are describing. In our case over here, it is a Howe (probably) center section ASA type chassis with most of the parts spec'd out, with price limits on things like calipers, shocks, rotors, etc. The engine rules allow a few different things, but most popular has been the LS1 ASA engines, making about 500 HP (or so). Since the LS1 is no longer in production, a LS3 version is being considered. I have built a couple of these from older ASA cars ( actually just sort of gone through them to be honest) and they are quite fun to drive, an excellent alternative to racing a full on Trans Am car if you don't have the budget. Right now there is a very cool looking Camaro body available, and we hope to have a Mustang and Challenger version out by 2013. As to the tires, they are a 15 inch bias ply, and only 600 per set.
Now, the used cars out there run about 25K or so, but as I understand it Bob Stretch and Greg Rodgers are offering brand new turn key cars for 80 to 85K.
Let me add I think all of this is a great idea, and I have some good friends who run them. But, if you are not willing to do whatever it takes, your going to lose whether driving a 10,000 car or a 300,000 car. That means putting racing first, ahead of weddings, graduations, family gatherings/vacations, and, especially, common sense.