Is this it Jason? Walmart.com: 26" Mens' Roadmaster Mt. Fury Mountain Bike: Bikes, Scooters & Skates
Looks like it will work fine. Specs say frame is "over sized" but you can work around that.
Also there is some great advice here, Pre-Motorized Bicycle Information. - Motorized Bicycle at Motorized Bicycle Forum
Think I started wanting to mount an engine first time I cloths pinned a baseball card in the spokes. I remembering wondering how to run one to the chain ring....