Since I wasn't able to get into the forum until a few minutes ago, I posted three other pics on the actual website. But anyway, I just found another car that I didn't add to my list. A 1955 Dodge driven by somebody who turned out to be the killer. So far, this is the best shot I can get.
What little I was able to get of the yellow late-1950's Ford Ranchero.
Sorry I wasn't able to get the 1955 Chevy. Also, I'd love to know if the Ford/Boyertown hot dog truck qualifies strictly as a background vehicle? The cast did hover close to it, and in at least one scene the star actually bought some food from it.