I have pumped hundreds of gals of diesel from the same style fuel tank that Cat put there name on. But maybe the tank was up on a mound at that ranch and gravity feed the O'l R4 D6. I do have rotary pump that I used that is the same anyway.

Yes with further thought, gravity feed with a gate valve and a whole bunch of turns to open or close. Good thing it was 20 or 30 cent a gal days.

Anybody have the answer to what is on the wagon in the last picture. My guess is in the oil patch, but just hauling thick crude that needed heat, or just moving a boiler to different location. So anymore educated guesses?

A steam boiler, sometimes for steaming a well or running rig engines or winches.

i have the same fuel tank, it has a cat fuel cap on it with a dip stick/ fuel level on it