87GN - Otto is correct that the original truck standard equipment came with the one tail light assembly for the drivers side. The license plate on your 1955.1 would have been illuminated by a light that's parts of a separate license plate bracket (not attached with the left brake light assembly which mounts to the bedside stake pocket), mounted to the left side of the rear cross sill for 1954-59 stepside trucks. There was a Right Hand "passenger side" rear light assembly (GM#986907) offered as an "accessory" that truck buyer could order and have installed on the truck by the dealer. Also available was a dealer installed accessory turn signal kit, if one was desired.
I know that a single taillight assembly is period correct, but in today's driving having two (or more) taillights is really a necessity for safety sake.
Many of our regular vendors offer both the drivers and passenger side taillight assemblies, as well as reproduction brackets for both sides.
The Jim Carter offered light assembly mentioned by Kevinski can be found as
LG157 - same fixture for the right side, so if you want that order two (2).
The Jim Carter offers taillight brackets as
LG149 (left) and
LG163 (right). Note that the LG149 left bracket does not include the license plate bracket. To get the separate license plate bracket with license plate light, that's Jim Carter part
LG283.
As mentioned above, there are lots of other vendors that offer these pieces, some fancier (chrome, etc.) and more expensive, but I think these Jim Carter pieces will fill the need.
Let us know how things turn out. It would be a great update to your
Project Journal.
