A War Office specification was issued for a truck to tow 4.5", 5.5", and 6" howitzers. It needed to have enough room for the gun crew and ammunition.
Later production trucks had a hatch in the top of the cab for air observation. When not being manned there was a canvas cover for the hole.
Wooden timbers made up the body with a dropping tail gate and a side door for the gun crew. In the floor were runners so that ammunition could be easily unloaded.
The cab's construction was steel sheets over a wooden frame.
There was a 7 ton winch that had 250' / 76 m of cable.