Old 84 chevy farm truck loses oil pressure

This truck periodically loses oil pressure once warmed to operating temperature. I saw dash gage be intermittent and always thought it was electrical issue, or sending unit issue until last week it dropped out for longer and engine developed ticking, and eventually knocking. I check the oil level almost every time I use it, and it was half when this last bout happened. I have since overfilled the oil in hopes that the pick-up screen unit may have come loose, but last two times I ran engine (too scared to go anywhere) the oil pressure showed 40+, then drops off entirely after engine is warm. Start it up next day and have good pressure until warm again.

I know I have engine damage, rod knock, and am in process of looking for a used 350 at present, but was wondering if anyone else can advise me of what has happened.

Probably wiped a bearing or the oil pump got weak.