I really should get my old SD car to the track sometime. Just spend the $100-$200 it would cost me to run it, cause I know I can pull a 13 out of it. It's no faster than it was stock with 160k and a Z spec pushing the 2.73's in the back.
All I have is a Gtech time of 14.19@103.8. The car wasn't setup to really run, had it been I would have gotten a high 13. The mph is generally 3-4 high on the Gtech.
As far as dyno numbers. I don't trust them. There are too many shops out there skewing the information to trust the numbers are accurate. There is no way in hell a stock LS1 will truely put down 320RWHP.
If it could, it's trap would be in excess of 110mph. It should also be running mid 12's if not better.