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.