Cory, get yourself a long piece of wooden dowel, or perhaps a cut off section of a broom handle (works good due to the rounded end). Press one end into your ear, put the other end on various parts of the engine with it running and making the sound. What you're doing is using it like a stethoscope. This will help you localize where the sound is actually coming from, be it near the rockers or down in the block. That'll tell you something about possible causes.
I'm in the process of a rebuild on my engine and this time I used one of the new 1-piece rear main seals from BOP. Your leak might be the seal, or it also could be the oil pan gasket. I shot some video of installing the BOP 1 piece rear seal that I still need to edit together and post. It's a very good solution to one of the "main" problem areas in Pontiacs.