'55 2nd to '87 are more or less identical. I beleive that there are some differences in the cross sills and the wood for the floor, so expect to have to relace them to get a proper fit. A ggod place to check on what exactly is different regarding the sills and wood is Mar-K. They have diagrams of most all years of the beds and what components are used with which year. They also have complete beds (minus fenders) if you decide to go thet route.
