I guess there's nothing more "period correct" than watching old films of when the cars we love were actually being used.
Here's a great old film about the Bethesda-Chevy Chase Rescue Squad. While other vehicles are shown, the "stars" are 1941 and 1950 Superior/Cadillacs:
[ame]http://www.youtube.com/watch?v=D882Y5UEOR4[/ame]
Here are links to the BCCRS website...:
http://www.bccrs.org/
...and its history section:
http://www.bccrs.org/about/history.html