As far as I know, the GT (2005, at least) does have a rev limiter. I've never heard of it being set low for a break-in period, though. It's set at red line, or a little over. I've bonked the rev limiter at 110 in 3rd gear, which is a weird feeling! And not in a good way, since I think it cuts the gas to the engine. Mind you, I've heard it's a good idea to keep the RPM's under 3000 during whatever break-in period you feel is appropriate. I did that for the first 1000 miles, and it was really hard!
You can remove the speed limiter with some tuners, though. That was one of the first things I did when I was playing with mine (a Diablosport Predator).
2005 Mustang GT in Torch Red
C&L Cold Air Intake/Diablosport Predator Tune
Tokico D-Spec Shocks & Struts
Steeda Sport Springs/Front and Rear Swaybar/Front Swaybar Brace/LCAs/Adjustable Panhard Bar and Brace
Steeda-branded Borla Stingers
Steeda Underdrive Pullies
1965 "GT" Logo and some other chrome bits