I just clicked on NWMules photo. The trucks in the photo, is not a WC52, but the short lived WC55! They have already had the 37mm cannon removed, converting them back into WC52s. They have also had the ammo storage racks removed from the storage boxes, that would explain the open boxes.
Things in the photo that point to the trucks being WC55s: short troop racks, no spare tire carrier, chevron run flat tires, no covers on the storage boxes, as an ammo box/rack fitted into the compartment to hold the rounds for the 37mm cannon.
One of the few, Frank USMC RET
PS. That is a great photo you displayed, NW Mules! I have never seen that one!