A nick in the gasket at the distributor will send lots of oil down the rear of the engine if the engine has a fair amount of blowby. Ask me how I know. I also changed the rear main on the same engine that had sat unused for almost 10 years. Seal was hard as a rock. I lowered the mains a couple of turns to help the seal come out. Put in the new seal and new pan gasket. New leak now. Front pan seal was too thin
, needed the thick one. Maybe I can brake clean it and silicone it.
Then I started to over think everything. Did I torque ALL the mains, or did I miss one???? Pull it apart and check. Everything was good.
Thick pan seal and all is well.