Rather than "Dodge" of "Plymouth", I'd just say "Chrysler-built/powered" as Plymouth would have gotten the bid over same-spec Dodges, typically, unless there was a reason the slightly longer wheelbase Dodges better suited the area the vehicles might be used in. Each had their own advocates, back then.
Ford had some credible cars, too, with (typically) 390 4bbls in them (which almost universally meant their full-size cars).
When I saw a city have Chevys or other GM lines, I knew they obviously didn't have much crime in that area. NO need for high-speed pursuits, obviously, unless there were FEW turns to navigate. OR there wasn't a Chrysler Corp dealer in the area, and they must not have liked Fords much.
Municipalities could sometimes indicate which brand of car they wanted by the way they built their bid specs, by observation.
CBODY67