I have a converted MGT and I'm running it with an 8XL. It's plenty of motor for the truck and I'm only running 4S with a Mamba Max controller. It'll flip the truck on its lid and then bounce back onto its wheels. My son drives it up trees and does back flips off of them. I've you are going Lehner, the 1940/8 should be plenty for a 4S setup. If you go more cells, you can just go to larger motors with lower kv ratings. Personally, the 8XL on 4S is more than enough for a basher with huge tires on it. It only does around 25-30mph, but it gets there in the blink of an eye and almost nothing can stop it.