That was originally a roadster, converted in the 40's to a truck so they could get more gas. Trucks were allowed more gas than cars when gas was rationed. Not a kit, converted at home I would assume.
During WWII there was gas rationing. Since pickups were considered commercial vehicles and necessary to keep the country running they weren't restricted to the gas ration plan. So many guys did just what you see there. There were kits available and of course many guys just built their own. My 5 Window was one that was converted and they cut the rain gutters out of the trunk to make it a little bit bigger!
As mentioned above, it was fairly common. Attached is a photo of a coupe, still in service, hacked up the same way. In the '40's, Studebaker had a factory-option of a slide-in bed for the coupes that replaced the trunk lid.
The Jalopy Journal
