This Willys-Overland Fire Pump needs an L-head, but it seems an unusual item. It looks like the trailer was not original to the unit, based on these two photos from G503:
https://www.facebook.com/groups/WillysSwapMeet/permalink/2800695516870376
“1943-dated Willys American fire pump. US Army Corps of Engineers, 250 GPM.
“Willys American” cast into the pump body. Enclosure is gone.
The base is the fuel tank. Mounted on a 2 wheel trailer chassis with antique tires and 2” ball hitch.
No suspension and old tires so needs to be hauled on a trailer.
Has WWII OD paint under the red paint.
I removed the engine and bellhousing for use in WWII jeep restoration. Selling with the engine front plate, manifolds & carburetor, governor, oil filter & bracket, fan and fan shroud and generator. You will need to supply a Willys L-134 motor and bellhousing to put this back in operation.”