You can cut down early Falcon tail light lenses to fit in the stock bezel, they have a dome/bullet shape kinda like a 56 Olds taillight but way cheaper. I can take a picture if you want, that's what I did on my '53 and I like it. The Olds tail light lenses also fit in the stock bezel and are very nice looking, they were popular in the 52-54 Ford cars back in the 1950's already.
Here's a trick I used in the early 60's. I cut the center out of the stock lense turned it around and put a red bullet shaped lense in the hole from what was the front, use longer screws and attach. No body back then ever figured it out on their own as to the origin of the lense.
Moon makes frenching bezels for what its worth. Atleast, they used to, and I think have stopped making them, and are just selling off what they have left. I'm running tunnelled '59 caddy lights in mine. I also like flat plastic tailights for these cars.
Resess A 59 CADDY Taillight in Each Side.. that would look sweet.. maybe bring out the taillight pocket a little bit.. with no chrome rings showing..
I had a set of those, from a '54 Jet that I thought I would use in my '53. Ended up doing the cutdown lenses but I like those Hudson units, very clean looking. Also hard to find unfortunately, mine went to a Hudson restorer, they weren't that great but he seemed thrilled to get them.
I popped these trailer light covers over my stock taillights for a different look. The best thing is they were only $1 each. They fit like they were made for the taillights. Not the best pic but you get the idea.
These are Frenched and tunnelled about 7 inches. I really like this look, but Olds look fine. Excuse the poor molding work, I was in a rush.
I have a pair of the 56 Olds taillights. One is a NOS Guide and the other looks aftermarket with a slight ding on the very tip. I was going to use them in my old 54 Ford, but I sold it a couple years ago and I have parts I am offloading.