TomE from the CF came to Pomona in his red Z06 in August. I raced him in my GTS and ran a 12.5 to his 13.0. I think he ran a 12.8 by the time the day was over, and I ran a 12.4. This was stock vs. stock. Now Tom is running 12.4's with Halltech, and I'm running in the mid-11's (on ET Streets).
Since I own both, here are my observations: for stoplight-to-stoplight races or 0-60 runs, the two cars are very close, primarily because the Viper is a b**** to launch, especially with the stock 3.07 rear end. Too much throttle and you leave hundreds of feet of rubber down the road. Too little throttle and you bog. The best 0-60 time (G-Tech) I've gotten on the Viper with street tires is 4.22 sec. Best with the Z06 is 4.15 sec. So, for short-distance races, it's really going to come down to the driver. I don't doubt that Dave beat a Viper at the track, but I bet Dave drove better than the Viper guy on that run.
If you drive the Viper well, you can run 12.0's at 118 mph very consistently (in stock form, at sea level, etc.). I am not that good. Some Viper guys have gotten as low as 11.8 in stock trim. I just don't think the Z06 has the kind of top-end the Viper does. My Z06 certainly does not, but I got one with a "bum" motor (only 336 rwhp!).
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[*] '97 GTS Blue/White Stripes (Borla cat-backs & headers, smooth tubes, K&Ns, BTRViper half shafts, MT ET Streets, 456 rwhp, 490 rwft-lbs, 11.7 sec at 120.3 mph)
[*] '01 Z06 Black/Torch Red Trim (Bone stock, 12.8 sec at 111.2 mph)