My 02 Z28 M6 in factory stock form with 16K on the clock ran a 12.99@109 with a horrible 2.01 60' on the stock goodyears hunting for traction through first and most of second. The dyno at this point was 315/333
With a lid and catback and better tires I ran a 12.68@110 with a 1.94 on better stock size tires. Power at this times was 326/341
I now have a very mild Z06 cam in it and 275's on 18" heavy ass Boyds and I have yet to run it because of the winter but I would expect with the cam and better rubber even though they are heavy I should turn 12.2 or better. If it wasnt for my weak ass rear end I would put slicks on it and run hig 11's like my friend chris in his 01 Z28.
My 86 Mustang kills my Camaro off the line and through the 1/4 mile, it runs low 11's and makes about 440 rwhp. The mustang on the highway has nowhere near the top end grunt of the LS1 due to gears and from a 60-100 roll we are almost even, the mustang about 1-2 car lead at the begining with the camao at the bumper at 100.
You have to remember all LS1's are not created equal, my times are somewhat unique althought there are many people that have duplicated or beat my times. The A4 launches sick and is easy on the rear so it takes more power to break it. The M6 traps higher and is a highway beast but you cant preload the suspension much to get a great launch.
All years are not equal and not to go into too many specifica the 01-02 models are the fastest from the factory and have the most power.
Modded is a different story, my buddy has a built 346 (LS1) with a 2 stage shot and he runs 9.30's on slicks and a no interior car with a 3 speed auto. He is almost full weight and has a lot more to do like K-member and lexan windows...etc.
I have had one really close race with a guy in florida on the higway. It was on 02 stang with a v2 and 4.30's he said. From 60-120 I only had a car on him when I was stock and I only won because of his gearing and how often he had to shift.
LS1's are tough but not as unbeatable as you think!! If you have a well set up suspension and know how to launch you can get a great jump and as long as your not running the full 1/4 you should beat him with some mods if its a light to light street race.
Good luck it does take money to beat stock LS1's and lots of money to beat modded ones.
Get an 03/04 Cobra, pulley and be done with it!!!!