I've hit the speed limiter several times on my 02 GT. It stops at about 148-149MPH. I read on an on-line spec sheet that the speed limiter is indeed 148.
If you have gears other than the originals, then you'll see the car hit 150, and keep pulling because your actually going slower than what the speedometer reads. I do know you can have the speed limiter removed though, I haven't tried it, and I don't think I ever will cause I don't trust myself. As soon as I hit the open road, I'll push the car to its limits.
That's not always a good thing, atleast for me. I already bent a few valves from red lining the car so much.