We have had this discussion on this site many times before, as well as a thread to post photos... but many funeral homes, fire departments, and rescue squads took a basic station wagon, put a cot fastener in it, put the stretcher in it, and crammed first aid supplies in it and called it an ambulance.
It was economical, and saved wear and tear on combinations and straight ambulances. A funeral home in an adjacent county ran a white Vista Cruiser wagon with a Vis-A-Bar light on it up until they quit running ambulance service. I can remember well the brown Buick wagon the rescue squad had here when I was a kid.
Supervisor's car? naw... it was the 60's... you could run whatever you wanted as an ambulance and a station wagon fit the bill...
Ex western NC unit from a fire department...