60 mph mamba brushless setup for e-maxx, would this work?

Sorry, it still seems like twice the expense to me, for no reason. Any added benefit that you get from having the two motors will be negated by the the parasitic effect of the extra weight and the fact that both motor/esc setups won't be running completely in sync with each other. Aside from that, I don't think that you'll ever get that muc power to the ground.

Take a lesson from the drag racing guys. It's all about reducing weight, not necessarily adding power. Many drag racers that I know opt for the MM 4600 or 5700 motor with moderate gearing, rather than the 7700.

Your setup will look cool though.