The 2nd gen 4x4 bed has about an 1.5 inches wider fender flare then the 2wd beds, other than that the bolt patterns are them same.
If you can't locate a 2nd gen bed, 1st gen beds will also bolt up w/just a little bigger gap between the cab and bed then w/a 2nd gen bed.
'80 bed on '86 2wd.
