Stock LS2 engines are used in some aircraft. The engine itself has the ability to go a little over 400mph. The only limit to that is the drag coeficient of the vehicle it's in. I'm trying to remember the magazine and article I was reading to give you a good reference, but it hasen't come to me yet, but the GTO has the ability to reach speeds of the low 200's with very few mods. Removing the limiter is a given. The other mods I can remember are a functional spoiler on the rear of the car, functional air dam or spoiler on the, roof, air must be allowed to get to the brakes, lower the car an inch, change all of the suspension parts to a stiffer one (like Koni), and 9 1/2 inch drags radials in the back. Im not sure if street DOT's are rated for speeds over 200mph or not. I work for an automanufacturer. I learned there that a cars top speed limit is set to the tires ability to handle that speed. The tires used are based on the design and purpose of the car. For some reason, GM always cheats us a little. They always seem to use year round alweather tires on even their muscle cars, so there's a little room to play with. Z rated tires are designed to handle speeds over 180mph, but I dont know the limit. There's a guy in Austrailia who took his GTO to 212. The front end of the Austrailian GTO (not the Holden Manero, but an actual Austrailian GTO) was just a little different than ours. It looks much better. It has stacked fog lights.