TL, Those are 53 Pontiac station wagon tail lights. They may be scarcer than Packard lights. The wagons usde the same quarter panels as the Chevy wagons so they designed a tail light to fit the Chevy sized hole. 53 and 54 Chevy tail lights are the same size. I don't like the 53 version the 54 lights look nice though. I think I have a set of 54 lights around here somewhere but the chrome is pitted. If you're going togrind off the chrome and french them they would work good. The bottom half is a clear backup light but they sell custom lenses for them that eliminates the clear lens.
Some people use two pair of the Packard lenses and butt them together to make a boomerang shape lens similar to a 60 Chrysler and make their own housing.

Suedeplymouth, Those Packard lights work on a 53 Plymouth too. You should get them before somebody else discovers them. If people have trouble identifying your car now they'll really be confused with those lights. Check out the engine while you're there. They were wicked fast in a heavy Packard and would make your Plymouth fly.