I thought I answered this post already but I don't see my response.
Nobody said the GN was stock. Various people have pointed out these cars run around a 14.0 flat in stock trim and the rarer and quicker GNX still is only mid to low 13s. A GTS even with a bad driver should crush one easily.
But the camera car (also a GN) which walked on both the GTS and the visible GN had to do a burnout before starting so I don't imagine it was on the stock 60 series radials, and the exhaust did not sound like mid 80s vacuum cleaner.
If he has drag radials, 112 octane, and 20lbs of boost his car is capable of around a 12.0.
http://www.dragtimes.com/ This isn't a big secret. Same as the TT Supra. The cars come with big turbos and decent fuel delivery from the factory and once you screw the boost pressure up, they go. Internally stock means inside the engine, not that the car isn't running 10 more PSI than it came with out of the factory. Except for the fact the camera car had to do a burnout we really have no idea how modified it may have been so it could have had forged internals, aftermarket turbos, ported heads etc.
Now the GN that is visible is running skinny looking tires on what look like factory rims. He did not do a burnout and does not look like one of the scary fast GNs. Since it isn't possible for a car to run low 12s on 60 series radials I have no explanation for how the "race" played out between him and the GTS. Except the Viper did not hammer the launch, the 1-2 shift was slow enough you wonder if his clutch was bad, and the guy had his elbow hanging out the window like a Friday night cruiser. My guess is the GTS was not representing well and was on his way to a 13.0+ 1/4 mile before he wisely pulled the plug. Maybe some kid who borrowed his dad's car and didn't know how to drive it. Figured all he had to do was show up in the Viper and the race was won. Whatever, he looked like he was having problems.
I don't think most GNs are modified to run a 12.0 or quicker but there may be thousands that are. These cars almost all belong to collectors or racers.
The thread was "86 Grand National beats on a GTS???" Go post the qustion in the Viper Racing Forum "Is it possible for a modified street legal Grand National to beat a stock Viper" and check the responses. THEN post te link to the race.