408 oil pressure issues

Background- '72 360 based 408 with newer oil pump/pickup, 360 car pan and dipstick, '98 magnum heads with a hydraulic roller.

Hot oil pressure gets low. It's been a few years since it got together and it hasn't seen many miles but it looks like I may have painted the oil filter mounting plate as I think I found paint flakes down there. Motor sounds better and quieter than my low miles 3.6 so I suspect no engine damage. I think we have a high volume pump in it so I'm thinking the Canton Racing plate may help resolve my issues but I wanted additional input. I was able to pull the adapter fitting with a 3/8 extension after I nicked it up some with a 12 point like a fool. I may pull one from a 340 or another 360 I have or replace the fitting. Looks like the old gasket is still hanging out there, but I have the Canton to replace the adapter. Mostly I'm curious if there's something else I may be missing causing the drop in hot oil pressure. I did not have a gasket/washer between the bolt and plate though.

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