IIRC the earlier cover had a hole for the crank case air recycling. I retrofitted my '85 to a tbi from an '86 and swapped the valve cover. If the question is what fits, I believe that at least thru '91 will fit on any earlier model. I might have one sitting in the garage that you can have for shipping.
Hoss
Edit. You might think about retrofitting a tbi into your rig. I did everything I could, cam, header, bore, porting and got the most bang when I retrofitted the tbi. That carb is just crap. I wish I could have found a mpi to fit but could never find one in the junkyard. I loved my 4-banger and would still have it but the son drove it through a deep mudhole.