the stepsides are repro'd because they fit 20 or more years of trucks, but the 58/9 fleet is unique to those years, and not a huge number of them made - every other series of fleet is specific to the years as the bedsides match the feature lines on the cab - I found a NOS 58/9 fleet bedside a few years ago at one of the body metal suppliers . . . . . $1000.00 for the drivers side only - that'll buy a lot of time at a bodyshop!
Bill