75 and older LUV motors are not at all compatible with 76 and newer G180s and G200s. The block and head designs are completely different. I doubt you'd find two bolt holes that would line up. You'd need a 180 from 76 or newer to match any G200 parts.
If I recall the G200 and later G180 are pretty much interchangable. There might be a slight difference between the size of the combustion chamber on the head, but its not enough to cause much problem if you put a 180 head on a 200 or vice versa. Hopefully Kuranosuke will notice this thread and give some details. I know he looked that very problem over in some detail when he built up the motor for his LUV. See his thread here:
http://forums.luvtruck.com/viewtopic.ph ... sc&start=0