There is a difference in profile.
Not sure if this is a CJ-5 to CJ-8 difference - don't see why it would be - but the '78 motor I have sitting here has a much different profile from any of the '80's engine's oil pans (4 in garage & 2 on my '82 Scramblers). The '78 sump is not as deep but overall appears larger than the '80's ones which are more deeper but overall smaller. (Oil pickup tubes may therefore be of different lengths.
Also, the '78 oil pan does not have a skidplate tack welded to lowest portion.