Attached is a picture that shows an open port in my engine.  Bruce said this would be used to return oil from the oil cooler / filter.  After finding a perfect metric to AN-12 fitting, I just found out that it won’t fit due to the mount.   In another thread, there was a picture of an engine, with all the holes labeled, and I noticed that it didn’t even have this port.  There was also no labeled port for returning oil from the cooler.  Do you just get it to the pan any way you can?  Of course now I have to find a plug for this goofy metric hole.