I know the Dodge Crews were factory-built, starting in 1963. I wish I'd thought to look for a data tag or a manufacturer's plate on the cowl or the doors, looking at that '61. It was still a cool rig! The back doors were like the fronts, except the upper door frame was squared off somewhat, with a roll-down window in the door and a fixed vent window at the rear of the door.
Now that I think about it, I worked with a captain at Tinker AFB, OK in 1988 that drove a '65 Crew Cab Chevy on a daily basis. It was a blue and white, 2WD, 283 4-speed long bed truck with a camper shell. Definitely not a homemade job! When he retired, he took the truck up to Colorado Springs.