8/80 believe the 4X/6X/7X shared rear axle brakes in the eighties or at least those with drums brakes. Only different is some do not have the hand brake but shoes and drums are the same. I have one post 8/80 with a hand brake but no sway bar tabs making from a SWB 40/42 series. Ten a later later one from a 47 series ith no hand brake but tabs for the sway bar. Other the hand brake both appear the same. The pre 8/80 4X series rear full floater I have has different brake then the semi floaters during that time period. Drums are finned for cooling and larger then the semi floaters. Believe the finned style came on LWB 4X series. What the lighter SWB 4X series got unsure of as US never got a full floater in any 40/55 series. Just curious if there is a lighter duty full floater that was used on the earlier ones.It's a pre 8/80 axle and it appears this does not cross to the 60 series but I could be wrong... Any clarification would help!