So far the the best solution is the Mamba Competition X(motor/ESC) this tiny brushless speed demon will propel your 1/18th truck to insane speeds.
The best brushed motor,not easy as I have not tested them all.So far very good choices are the Trinity Mass termination, one18h.com own Beast motor and the Orion Baja motor.All good motors
Make sure your gears are upgraded,the drivetrain is too.A the Competition X has so much power it will accelerate not only your truck but wear BIG time.
As a side note I am finishing upgrading my Mini-T Pro (all alu now,Dynamite alu parts) and purchased the alu upgrade for my new RC18T. Now these not only will look the part but hold to any micro motor out there.