I keep running into the 'must not be altered in width' issue. The car is slightly widened with the flares on the fenders and comp coupe or altered don't allow width changes, so I keep ending back at the circle track category that seems to accept this. It doesn't say they do or don't accept super chargers though, but says all engine classes accepted. Would this include super chargers?
Non-stock superchargers and turbochargers are fine once you're not running the car in Production--the use of forced induction simply changes your class from unblown to blown (so, for example, if you were going to run a naturally aspirated car in gas altered, you would be in AA/GALT (gas altered), but if you put a blower or a turbo on there, you would move into AA/BGALT (blown gas altered). If you check the records, blown cars are generally faster than non-blown cars (not surprisingly), so the record in your class (if you were after a record) would generally be faster. (NOTE: For SCTA (Bonneville), how you build your car (safety-wise) is based on the record speed in your category, NOT on how fast you think you're going to run. At Bonneville, if you're going to run in the G-engine class and you know you're not going to go faster than, say, 150, but the record in your class is over 200 mph, you have to build the car to over-200 safety requirements. LTA and ECTA, on the other hand, base their safety requirements on the speed range in which your car is going to run.
I agree with you that Circle Track could be the right category for you; there are a number of ex-NASCAR vehicles that run in that category. (Oh, and to clarify something I wrote earlier, you couldn't run your '72 Camaro in Gas Coupe (which is for cars 1981 and newer), but you could run it in Classic Gas Coupe.)
I'm not sure about the flared fenders--for that and all other questions, you should contact Steve Van Blarcom at the LTA or Joe Timney at ECTA. (And remember that you can also run your car at ECTA events in Wilmington, Ohio, which is about 200 miles farther from Ottawa than Loring...)