Brad,
Since those are not standard parts. it would be hard for anyone to assure you of what used parts might work.
By a "panel ambulance" are you referring to a rear door on a Sedan Delivery (car chassis) that was used as an ambulance, or a Panel truck that was converted to an ambulance?
There was a 1954 crew-cab conversion-vehicle. It had a different style rear side door/jamb. I do not think anyone has ever seen one, so I doubt you would ever find one for used sheet-metal parts.
