How would this be?

[BrianG]

That setup is a decent setup for moderate speeds (~30-35). But 45mph+ will require tall gearing and might stress the ESC and batteries to get there. For faster speeds on something as heavy and large as a Revo, you really want 5s or 6s on an appropriate ESC and motor. Gotta remember that the MM, 9XL, and 4s is just about the cheapest setup you're gonna get and will not have super high power like the more expensive setups.