Were those propane (LPG)?
probably - can’t recall
there were also capped oil wells on farms - capped because the production was too slow to make oil companies buy.
“Were those propane (LPG)?”
Probably.
My brother in law worked with a family that ran harvesters from farm to farm back in the 70’s. They were featured in National Geographic as a matter of fact back then. All the guy’s trucks were LPG conversions.
Hard on the valves though. Today with the hardened valves and seats due to unleaded gas it would be a non-issue on conversion.