In (mid?)1970 the rearends were widened about 1- 1/2,, 3/4" on each side, the later axles won't fit the earlier rears, then in 1971 they went 5 lug. The 5 lug axles to 87 fit the wider(post 70) rears & vice versa. 73-87 rear end will fit but require the perches to be cut off & coil perches welded on, same for 4x4(they had leaf). Same 6 lug pattern for 4x4(til 98??) & pre-71,,Clear as mud? brian
