I finally got the time to pull the engine back out of my truck and attempt to fix this issue. I hate trying to "fix" something if I don't fully understand the root cause, and lucky me, I found it.
I pulled the pan and removed the oil pump. Took it apart, removed the pressure relief spring, and tried to remove the plunger. It is stuck in there solid. The moron that assembled this oil pump had to have used a hammer and punch to get it into the bore, it absolutely will not come out or even budge a little. So, root cause: pressure relieve valve stuck closed, oil pump over-pressuring the entire system, and is likely pushing oil out the rear main bearing with such force it's blowing past the rear main seal. I have all the parts to fix it including a new oil pump. Will see how it goes in a couple weeks.
-JW
