The first one is the "Stump Jumper" M151 6X6
The rest of the pics are of the M151 6x6, all of these two models are manufactured by TNJMurray in Dover, Delware. US
Scroll Down and you can see these on this site.
The 6x6 was an experimental vehicle, designed to replace the 3/4 Ton vehicles in the US Army inventory, but never was incorporated, only a few prototypes were made