RANGER DID IT, PERIOD. STOCK RUNS
Its really kind of irrelevant IMO.
Track prep, wind speed and direction, temperature, humidity, barometric pressure, incline of the track (some are uphill or downhill), age of the tires, and a million other variables have to be "just right" to get that record run. Not to mention that his LS7 might just be a bit stronger than others (deck height, cam timing, and other things vary from engine to engine).
The best way to compare two cars isn't by comparing the outliners, its by comparing the average results. I think its pretty clear that in all tests of a Viper vs. Z06 on the same day, with the same driver, the Viper is a bit faster.
Anyways, it would be easy to give a C6 Z06 more power while looking "stock". Stock-class racers have been doing this for decades
I'd start with a sleeper cam and a reflash. Raising the car up as high as it will go (to improve weight transfer) and zeroing out the rear camber could help a lot too.
Also, it sounds like a stock ACR could run 10s more easily. Maybe I'll give it a shot when I get my car. The MPH probably wouldn't be quite as good unless some of the aero bits were removed, though.