Okay, thanks guys. I will study the rules for both classes as well as STX as another friend suggested.
Also, I ran across a forum entry where a guy said he was autocrossing a 275/40 on an 8.5" wide wheel. I would not have considered this due to rim width recommendations. Assuming the answer is "no" then if I was to choose between a 275/40 on a 9 or a 255/45 on a 8.5" wide wheel, what would be best considering the weight and lateral force of the front? I know I would do 275s if I can get some 9.5" wheels, but I don't know if that is "in the cards" for next spring when I plan to return to racing.
And (off subject for the SP forum) but I have to plan way ahead. My engine is fine right now and the car only has 86,000 miles on it, but it is a Northstar. I have to consider the cost of future replacement of the engine with a swap or a bullet proof rebuild. I was disappointed to find out that an LS7 is not a possibility with the transverse automatic setup due to the Y block. I am now thinking along the lines of the 100 pound lighter and stronger 4.9 but with the addition of the Eaton supercharger found on the GXP cars. It is a cheap mod and I could get back most, if not all of the 75 horsepower I would loose.... The other option is to turbo the northstar (only after a rebuild with head studs of course) or to find something else in the 450 lb Northstar and LS engine weight category.
If I am not mistaken, any of those mods would have me in SMF anyway..... 275 horsepower and 0-60 in 6.8 is not slow, but for that engine weight, I need more.... I initially was looking for the 4.9 powered Eldorado that has a 8.5 second 0-60 thinking that the weight savings up front was worth the power loss..... I just don't know now....
BTW ; I do plan to relocate the battery and maybe washer fluid tank to under the trunk floor. That will help some.