FWIW, the original owner of my 69 Z (Kym Miller) ran consistent times with the Camaro in S/S JA and did so for 8 straight years finally winning a Championship in 78'. He then setup a 70 Nova for the same class and took the winning drive line out of the Camaro in 1979 and dropped it into the 70 Nova, but never got the car to run as fast as the Camaro. Exact drive line, same tires, same everything thinking the lighter car would run quicker? Well it just didn't, and he said it had to be wind resistance and/or weight distribution as the Camaro was better on the track??? Just an interesting set of events.