The 81-mid 89 beds (we think) had brackets welded to the crossmembers for the bed floor that contacted the frame for support. The 1990-ish-1993 beds did not have the brackets, they were built into the frame when it was bent. Those are the only differences 81-93. They should not apply in your case. There was a older moparts thread titled 81-93 bed differences about this from 2010 or so but it seems to be lost