Emaxx questions

I have noticed that there are some people having heat issues with the 7xl, plus a 8xl on 4s lipo will be more than enough power for a regular emaxx, as this is not a race chassis or suspension. Also, i have noticed that the more a truck weighs, the higher the number motor one should get. My truck is not light. I don't see an emaxx being stable at much more than 35mph, so there is no reason for me to make it go any faster than that. Also this is my first stab at a large bl setup, and if i get something too powerful, there would not be much incentive in upgrading later.

One more question: what kind of pinion should i get?