Ideas on what's causing my click/tick/rattle noise?

I'm not sure now to figure that out? I had good oil pressure. When tearing it down I pulled the pan and double checked the torque on the rods and mains to make sure I didn't skip any and leave them loose - they were all spot on. Sadly, I didn't think to keep the rod bearings so they are gone now. When I built the motor, I plastigaged both rods and mains, they were in spec. The rods and mains were all still standard on the journals. I can verify the original main bearings were standard, I still have the old set. I'm quite sure the rod bearings were the right size (also standard). So far I got the crank back into the block and it plastigaged correctly with new main bearings. I mocked up the pistons with the new bearings and those also plastigaged correctly. I'm waiting for a new set of rings and I will install the pistons for their next go-round.
Well, I don't know man. SOMETHING happened.

I've often thought it sucked that the slant 6 is so difficult to prime. It has to run basically dry until the pump fills the filter and the engine finally gets oil.

BUT I thought of a way you can actually do it. It's a pain. With the camshaft in the engine and the oil pump in and filter on, you can spin the camshaft with an air ratchet and prime the engine. You don't want to use an impact of course. lol

I just slob lots of engine assembly grease on so the engine doesn't have a chance of being to dry and have at it. I've done the camshaft spin thing once and it does work though.