[MetalMan]

With smaller tires, the Feigao 380 size 6s should push your Rustler pretty fast. Or, if you want good speed, runtime, and power, you can get a Feigao 540 size 12s, and run it on 12 cells NiMh (14.4volts) or 4cell Lipo (14.8volts). This is the setup I run in my Rustler, and I couldn't be happier with the runtime and power.
Basically, you want the most efficient motor you can get, so you can gear it up more without it getting as hot. One thing to keep in mind is that higher voltage (when paired with a slower motor) will give better efficiency than lower voltage and a faster motor.