1969 Chevelle 454 Bottom Engine Knock

Hello all here are the specifics,

454 rebuilt engine out of a 1970 truck in a 1969 Chevelle, manual transmission, using heaaders, moderate cam, using 93 chevron gas. Ive put maybe 300 miles at the most on the car, have had it for a year in covered parking. i dont rev engine hard or taker her past 70 mph. I live in hawaii warm all year around.

symptom: was driving and knocking started. Watched Jeep video and sounds like that sound. Checked oil was at decent level. Lifted valve covers. Driver side, valve one, intake valve was crazy lose. Others were fine,. Rockers looked ok, passenger side was fine. Oil is being delivered via the push rods. sound occurs at start up and gets faster as rpms increase. Used auto stethescope to listen for noise, seemed to get more pronounced at bottom, but could still here a fair amount when i touched it to valve covers.

Here are my questions:

1.Would pulling spark plugs help me isolate which valve is making noise?

2.Can a collapsed lifter cause this type of noise?

3.If i have oil running through push rods could it still a thrown rod, or thrown bearing?

4.Can bad spark plugs or wires cause knocking, i noticed that some of the boots had been burned from touching the headers, and the ends of the plugs are rusty.

5. Could it be built up carbon on the pistons as i dont use car that often?

I plan on dropping the oil pan to see if i can see any metal or copper shavings.

Thanks in advances for all the help and apologies if these questions are newbish.

Kimo