So, if I understand you correctly, you have ZERO oil pressure, and yet there is oil coming from the pump at the filter location. Am I understanding you correctly?
If that is the case, then you have a MASSIVE internal leak somewhere, way more than worn bearings. Possible areas include a missing cup plug in the front, and the threaded plug in the rear of the oil gallery. Other possibilities inlcude a crack somewhere along a major oil gallery, but I would be at a loss to suggest where.
As for your theory of a plug somewhere, I really, really doubt that, unless someone injected super glue into your engine.
I have rebuilt literally dozens of those engines, and have never heard of a problem like that. I consider those lube systems to be fairly bullet proof.