AHA! Second time I checked with Monaco I was told to check the block above the starter... there it was. Now all I need to do is get a new sending unit and figure out how to squeeze in to make the replacement.
Perhaps the earlier ISL's, with a water filter on the street side, use the oil port above the starter on the curb side and newer ones use the port next to the oil filter. Had I known where the iol ports were it might have made the search a bit easier. Why Cummins couldn't/wouldn't answer my questions I do not know, they surely sold thousands of engines to Monaco...