I believe frame width and body mounts changed between generations. The best way to be sure would be to measure, measure, measure. Check the length from wheel well to bumper and wheel well to cab. Check overall width and length and measure mount location. If the wheels will fall in about the same spot, I may just be a case of fabricating mounts for the bed. Although, I'm willing to bet the older bed will be narrower than the newer bed. Hope this helps.
in process of puttin a 86 2w bed on a 81 4wd had to use the front mounts that drop down from the bed [they unbolt-or break off bolts in most cases] then split the longways braces and welded em back in where they need to go all other mounts fit perfect oh its a longbed too
