As far as I know they will interchange. The earlier 258s have better torque ratings than the later ones (due to heavier cranks, pre-'80). Oil pan shape might be different, but you could use your existing pan. Same with the bolt on motor mount brackets. The early one barrel carbs are no jet fighters, but mine works well on the trail and is as simple as hell. The earlier BBD two barrels are non-computerized.
jo-jo
'77 CJ5 Fozzy Locker
20 degree RTI 1250
jo-jo
'77 CJ5 Fozzy Locker
20 degree RTI 1250