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I'd start by draining the oil and looking for anything suspicious, i.e., contaminates or weird coloration. What your describing sounds like something intermittently blocking/clogging your oil delivery passage(s). My guess is that something has clogged the passage between the filter and the top of the block and has limited the flow of oil to the upper reaches of the engine which would account for oil starvation in a lifter which could cause the ticking. It would be especially pronounced at 3,000 RPM (which is, BTW, a pretty good buzz to maintain). How many miles is on this engine? What temperature does your engine typically run?

Look at this page for an excellent primer on SBC oiling systems - hi voluum oil pump installed now no oil pressure? | Grumpys Performance Garage

If you do find crud in your oil you may want to drop your pan and make sure the screen is clear. I'm not a big fan of "engine flushing" but some swear by it. If I were to do a flush, I'd definitely drop the pan afterwords and clean all the glop out of the pan and off the pump screen.

Others will chime in here. Let us know what you find.

Glenn