I just came across a speedometer, radio, clock and tail light identification website

even a chart to determine what car a Delco radio went into by the model number

just as an example, they have the way to decode a tail light by the markings on it, and identify the car and year it was on.

or look through the visual guide

so, for all sorts of helpful info on figuring out that junkyard, swapmeet, or atiic find: https://sites.google.com/site/identifyinginstrumentpanels/home
https://sites.google.com/site/taillightcodesguide/