Where is the leak?, oil after sitting for weeks/months Options

[fixer34]

This has been happening for a long time, but seems to be getting worse. Factory -6, while it is running and for several days sitting there is no oil leakage (OK, maybe a few drops). Anything longer and I start to get a puddle under the passenger side of the engine to the point that I place a large foil pan under the car if I won't be starting/driving it for a while. After a couple months I might have 4 quarts of oil in the pan. I know it is from the dry sump backflowing into the engine, but I can't tell where it is leaking. It is missing the heat exchanger because I don't get the burnt oil smell when starting the car.
Thoughts on where might it be leaking and can it be fixed without pulling the engine?
I was thinking about one/both of the oil return tubes, but figured they would leak while it was running.