Pretty sure there were more duelly farm & construction trucks than oil field trucks..... Brother in law has a 1936 Ford duelly spent its life in Virginia. They were used to haul heavy loads. I drove a 1 ton duelly dump truck in college for a job in IL. Almost bought a 1948 1 Ton International duelly in IL (Wish I had it was $800 back then).......... Friend has a 1952 Ton Chevy duelly but wants too much for it. It started life as a dump truck. Interesting it is 5 lug but heavy duty............