Long story short. I took my transmission out to replace my rear main seal. Easily completed that job. A day later I came back to put everything back together, and as I was putting the flexplate back on, I saw a drip of oil right under the seal where it meets the engine crank area. However, the rear main seal was bone dry.

So I thought, must be coming from the oil pan? No. Not the pan. Turns out it's coming from this seal that sits at the end bearing. In my Ford manual it illustrates these...

97' Mustang 3.8 - Need help finding this seal!