"They swear on a stack of bibles 235 is the original factory engine."
That mistake is understandable from a non-Stovebolt-devotee.
The 216 was not the first, nor the last, stovebolt engine size. The 235s were around longer, even though that includes seven/nine different styles/sizes of Stovebolt engines.
I just correct them in a friendly manner, and try not to go into esoterica. Usually these conversations are quite friendly.
"What do you tell them?"
Don, you could ID your motor and let them know what you have and what would have been original in your year/model truck.
I’ve looked it up. It’s a 216 and I think someone must have rebuilt it because it runs too well for a 60 year old truck.