My 49 sub has barn doors however all the hardware for the clamshell was installed in the body. The cables are there as well as the rectangular holes for the tailgate hinges just above the gravel shield between the body and the bumper. It did not have the barn door limiters that were supposed to be installed on the top of the doors that held the doors open. These limiters were designed to also position the doors perpendicular to the body so that the truck could be backed up tight to a loading dock. I found a pair in a local boneyard off of a panel that I will install when ready. In the case of my sub there is no way to know if the truck came from the factory with barn doors or if the dealer installed them, removed the clamshells and left the hardware in the body. I suspect that it originally came from the factory with the clamshells and somewhere along the way it was changed over to barndoors. One reason for this rationale is the lower hinge holes for the tailgate were covered with a welded patch and it was not a very good job either. The patches were then bondoed over and painted. Which brings up another question. When did bondo replace lead as the material of choice for body work? Weeds
