Yes, i have a 2000 GT and i'm saying the 5.0's are slow. They have some amazing potential, but stock, they are slow.
The 4.6 can be built up to handle just as much power as the 5.0 can. Personally i'm not a huge fan of the fox body style and the 94-95's just wouldn't do. I'll put my 4.6 against your 5.0 anytime.
mid 13's with slicks, exhaust, and an intake, maybe, but that isn't stock.
Also, you sure he didn't have any suspension work, built tranny, or rear end? He was running slicks, so i doubt it was his first time out and he had been into the speed thing for a decent amount of time. Most that end up going to the track and running slicks do some suspension or rear end upgrades, which would also not qualify him as stock.
So, since you have the guys motor you should have no problems breaking well into the 13's, so lets see those time slips.