Topnault has this steel bed replacement available. Says it fits 79 - 84. Other than mounting position what could the difference be?? I believe 79 - 84 only came in long bed versions. I know there have been issues with some of their parts fit and finish but not many options for a replacement bed. Really don't want aluminum.
tpautoparts.com
REAR TUB, FOR TOYOTA LAND CRUISER FJ45 , (STEEL)
Truck Bed, for FJ45 Toyota Land Cruiser
tpautoparts.com