This is more than likely non related to your issue but the 360 my dad had in a 91 truck was doing exactly the same thing. Pulled the pan and there was next to nothing in the p/u screen. Baffled I pulled the intake and found the culprit. I asked when he last changed the oil. " 10 years or so ago, I just add some when its low I don't drive it that much". The top end of the motor had sludged over all the return passages to the point the oil couldn't get back to the pan fast enough to be recirculated. I left the pan off and cleaned the top end up with kerosene, put in a new pump and its been fine for a few years now.