What follows was posted a while ago by Dinosaur. I copied it and put it in a file for future reference. It sounds like a good lead for you...
Those Merc WAGON taillights will fit all 55 and 56 Fords. They look really good in Fords, especially T-birds. If you do find a pair, yes, they will go for huge bucks. And then consider how nice they will be after all these years. Lotsa pits in the housings, lenses sun-bleached, and cracked. What are we to do? Go to www.leelenses.com They have some really cool tailights, and lenses. They don't advertise, I can't understand why. Anyhow, they have the Merc taillights in question, with or without bezels. The bezels are fiberglass, paint them and install. There are places that can chrome that stuff if you want, but I can't remember who. Anyone into the old vintage look should pay a visit to this site, lotsa neat lights. Oh yeah, the Merc lenses with bezels are $190, can't buy used ones for that price.
Dinosaur
Hope this helps! 