g'day mate,
the bullbars on the d21 do vary depending on year model. The d21 Navara from 1986 to 1992 has a different chassis rail to the post 1992 models. the 86-92 used the old Datsun 720 chassis which was narrower than the newer chassis. as for the 2wd vs 4wd the main difference between both types of chassis is that the 2wd's brackets sit around 2 inches lower.
hope this helps.
