Mopar Performance computers (PCMs) have their speed limiter set at 255 (basically removed). MP assumes that if you're going to buy a racing PCM you know what your limitations are in terms of tires, heat, velocity, and stability of your vehicle.
The rev limiter is still set (it's already higher for a MP PCM, but not unlimited), but that can be changed depending on application. Mike Leach, in association with Ron Zimmer, can provide those changes.