1956 Panel?

Actually, the first/factory single tail lamp/light is on the door. The other two tail/stop lamps are options are accessories/options.

You might have GM accessories/options or you might have other makes. What markings are on the lenses? GM dual lamps are hard to find and are expensive. They are sometimes available at swap meets and on eBay (high prices, if GM Guide?).

Maybe someone knows about period-correct reproductions, but there are aftermarket lamps that do not look original but they serve the purpose. Are you looking for single-faced or double-faced lamps?