RE: mamba is good...no?
5700 on 3s sounds good. Remember to put some good foam or street tires on there, and set it up with a bit of toe-in. If you really want to hit 80-90 mph, you're going to be going through diffs, spurs, pinions, and motors like cookies. If you don't have an adequate ESC you could cook those as well. If you don't get the proper batteries (big batteries) you're definitely going to lose some. Remember to weight down the front, otherwise you're going to wish you had some time on a flight sim.