60 mph is easy. You could go with a Neu 1512 on 5 or 6S and hit that while still being driveable. If you are planning on running off road tires you will have problems, though. Make sure they are CAed very well.
That helps alot. I will definitly be running street tires. I am looking to power the beast with two A123 6.6 packs in series. That way I can still use my Mamba Esc. Just got to find a motor I can run. I don't like the idea of endbell popping of motors.