[MetalMan]

That will be A LOT of power for a Stampede. I would suggest not using more than a L motor, as the end of the motor will easily get hit (even my S motor's end gets hit occasionally). A good motor for 12 cells is the Feigao 540 12s, which is a motor capable of pushing a light E-Maxx. This happens to be the motor I use in my Rustler, and on 4s Lipo in a very small space it pushed the truck to 56.5mph. On only 3s Lipo with conservative gearing (could go up 2 teeth or more and still have good temps) it hits 34.5mph. On good batteries, it will also wheelie (the lower COG Rustler) like crazy. This motor is lighter weight than the L motors, is less prone to being hit by something (from sticking out), and is still an awesome motor.