Well, it seems like gearmotors to fit this truck are made from the rare material
"unobtainium". I only found one that would work and is a little to fast but I think it will do. It is to long so I had to get creative with the rear wheels but I have it worked out. This is the complete set-
The gearmotor extends all the way thru the inner wheel-
Here is rear wheels assembled-
I have more holes to drill and tap and I have to make a hub cover. I am using 2-56 screws. I tried the 0-80 screws but could not tap the holes. Broken taps,stripped holes, ruined wheel-disaster! But the 2-56 size is working good.