Has anyone heard of the M-274 Mechanical Mule?
Its a 4x8" Platform "ATV" With a drivers pod on the front.
2 Cylinder Engine, solid axles, really simple.
Used in the Vietnam War.
It can be used for cargo, or it had a 106 mm recoilless rifle on it. 
For a beginner, building a 1/6 or 1/5 scale would be super easy.
Here is a Google link to a bunch of info...
See what's free at AOL.com.