From all the family accounts of it, the "modern" design change did have a lot to do with the trade in. (And the reason they held on to it) No options were included at the time, but the truck does have a heater in it.
He may have added it later for heading out fishing and hunting on cool mornings. It was used on the farm a few years, then retired to the task of hauling a john boat to fish for about three decades.
I hope some of my kinfolks can drag out some old pictures of the truck in "action" some of those years. That'd be really neat to have.
Thanks!
