Hi Matt, lets try it again, now with more information! If you use your 89 Firebird with SBC (if 500 cars came that way) and you use a non-stock supercharger, then you would be a B/BGC (because of the non-stock supercharger) or if you use the 89 Firebird with a V6 with a stock turbo then it would be E/PS like John Rains 297mph 89 Pontiac Indy 500 special with a Buick V6 with a stock turbo. John used the Pontiac with the Buick V6 with 40+ lbs boost for around 1200+hp for a top speed of 297mph and he is still trying for 300mph, his car is the most impressive car I've ever watched race!!! He also bored the engine from "E" size to "D" for more records in Production Supercharged. I raced my 1963 Avanti against him 7 years ago (my car was D/PS) and when my car was going 198 mph his car was going 276 mph at the time, so I knew my less aerodynamic car with an old Studebaker engine would never be competitive to John Rains more modern aero and more hp car, so I started the new racing class with SCTA called "Classic" now I can be competitive with the less aerodynamic muscle cars from 1928 to 1981. Good luck, Dave