I bought my 99 w/ 3.23 gears, in late 04 and it was bone stock. I took it to the track and ran a 13.6/103.

 

Looks like stock LS1's and Stangs are pretty much even. Mine ran a 13.42 @ 101.80 mph with a crank pulley. Probably would have been 13.52 without the pulley.

 

I don't think so Larry if you look at the vast majority of times 'stangs
are putting down. They are generally in the high 13's at low 100 trap
speeds. LS1's have potential to run low 13's at high 10x traps.

They're close, but the edge is definitely to the LS1 IMO. Who am
I talking to though? You know as well as I do.

 

Yea, I know....my run was on a cool night, with an underdrive pulley, with spare and front sway bar removed. And the two big heavy chunks of steel on the rear axle. I would say your "bone" stock LS1 or mine back then would have the edge over my 3V!

Reason I know for sure, I had a friend that had me drive his LS1 "bone" stock with spare and nothing removed and I ran a 13.2 in his car. Air was fairly good that night but I don't think quite as good as my 13.42 with my Mustang.