Here is another wild guess
I don't know my trucks history
But it was a red truck. With red horn, red fender braces, red air cleaner.
I think it was ordered by a government agency like a city truck or maybe even a fire department.
It has a hole for a spot light on the drivers side.
I think fonzs truck was a highway county truck.
My jelly doughnut guess is that chevy trucks ordered by government agencies had the passenger side drilled for a second data plate for gov ID.