I'm still confused...... are we saying that there should be two plugs in the same hole? Because I have one plug in there that is driven about 1.5" deep. You can see the shoulder of it in the top picture. The other plug doesn't even fit tight. It just drops and hits bottom. Besides that it looks like if I installed it it would only direct flow from the oil pump to the rear main.

I checked the other bare 350 block I have and there is only the one that is about 1.5" deep, not a second one, closer to the deck.