I ordered motors (E-150), a left and right gear box, and an AmpFlow Speed Control. All of these parts can be bought from Battle Kits (http://www.battlekits.com).
Why?
It goes back to my attempt to get all off the shelf parts for this and adopt the KISS (Keep It Simple Stupid) acronym. I want anyone to be able to go "click click click" the with minimal tools build this.