Name that knock- Solved

It's definitely more pronounced down low, oil pan area or further back. I poked around with a long piece of heater hose to my ear and crawling under the car it's definitely much more audible.

Revving it I don't hear that decrease in noise when it settles back to idle. It seems persistent. I also pulled the fan belt and the old mech fuel pump to rule out alternator, water pump, and fuel pump.

I need to rule out flex plate and bolts. I built the motor with a new SFI B&M flex plate and ARP converter bolts, secured with loctite, but something may have loosened up. Oil pressure also holds steady when I lightly rev it.

This sucks but hopefully I don't have to pull the motor. Thanks guys!