I never saw a stock GN run in the 12's. Back in 1987 my brother in law bought a 1986 GN. We took it to Lapeer drag way here in Michigan. He also read all of the hype about how fast a "stock GN " was supposed to be and thought he was going to blow my doors off with his "12 second" GN. He ran a bunch of 14:60's and a few 14:50's and was very disappointed. It was a completely stock 10,000 mile car. We had some stock GN's run low 14's. Most stock cars are not fast as people think. The stock muscle drags are some of the most finely and highly tuned and blue printed vehicles around. It is truly impressive to watch them run.
I had a co-worker with a GN that went on and on how fast they were. "We should go to the track" I suggested.
I brought my stock 318/5 spd dakota club cab. First race I beat him by a fender. Embarassing.
It was guys like that why I kept my T-type stock appearing. In the pits they tell me I need to add this or buy that and then when I tell them what it runs, they go "oh, nevermind".