The black paint on the 80’s engines makes it hard to find the leak.
My 83 D150 with a tall Wix filter takes 6 quarts at an oil change to get the oil to the full mark on the dip stick. Does the vehicle have the correct dip stick? Maybe you are over filling it?
The oil passage that runs from the rear cam bearing to the rocker arm rail runs through the head gasket, but that head gasket seal area is well within the head gasket perimeter and is not a typical leak area. And if it was the issue it would be leaking all the time the engine is running. it is not uncommon to see an oily film along the pushrod - lifter head to block joint. (just below the sparkplugs) That joint is pretty far away from the head bolts for direct clamp loading, but that is not pressurized oil, that sees only crankcase pressure.

Try power washing the engine and under carriage real good. Drive a couple 100 miles, maybe find an empty parking lot and do some turns and stops then re check with the UV light.

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Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

Bolt in the alternator bracket goes into the lifter galley. That can run down that side to the oil pan rail. Clean it well, drive it and park it on a large piece of cardboard overnight check go drips in the morning

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

There seems to be a leak at the head gasket on the back passenger side of the engine. From #5 cylinder to the back. The block is shiney with oil there but it doesn't drip. Drivers side looks good and dry. Alternator, fuel pump, and oil pump looks good. It is hard to see with a black case. Pictures don't show well either.

I have noticed a recent reduction of oil use by about half. I did a piston soak with B12 overnight. Didn't drop right away but the 3rd trip or so after that the oil use is a lot less. Still would like to figure out what is wrong before pulling the motor. I know the problem will show itself or get fixed with new gaskets though.

It still smokes a little when cold. Not at startup, just accelerating. I'm guessing the rings are weak and not wiping the excess oil off until it warms up and thins out.

Thanks everyone. Will update here when/if I get the motor out.

The head gasket on the passenger side is very narrow along the lifter galley. It is not unusual for them to leak there. You can try retorquing the head, it may or may not work.

I have had good luck spraying the area down with brake cleaner then sealing the area with good silicone sealer until the gasket can be replaced. You also have to be real careful when installing the head because it can catch the gasket in that area and cause a big leak.

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Official Cookie and Mater Tormentor.

I would try the B12 again... or what ever that other stuff is in the white can with red lettering. Maybe put the stuff in, and spin the engine over with out starting it... let it Sit overnight, spin it over some more, and put the rest in the fuel tank.


Also:
I've successfully used "restore" snake oil in a can years ago on a briggs and Stratton powered pavement roller that smoked blue clouds and made people complain of how I smelled like smoke after I sat on it for a morning.. it cut down on the clouds of smoke, it still smoked but more like a two stroke.. (and I didn't want to keep breathing oil smoke for that particular employer)

AND I have used the same In a Mercedes diesel that was tired enough that it would not start below 32*.. with the said snake oil, it will start at 20* if I get the starting procedure just right.