Calm wrote:
Drain your oil and open your filter up.
Check for any filings.

I know it's a long shot (a bad shot at that ~sorry~).....
but I had the same noise (sortta lifter/sortta tin like tapping) on my LT1 last year. Was coming from the rear of my intake. Stethicoped everything (intake/VC/heads/block/pan) and the loudest was up top in my intake. I thought it must be a rocker so adjusted those. Noise persisted after, so then I thought perhaps the oil pump drive gear (like your dist. drive gear). Never opened it up though.

Anyways, few days later oil pressure dropped a little (normally 45.....dropped to 35 or so).....The tapping noise was getting a little bit louder, but still only from the intake area. So I pulled the intake but everything 'looked' fine. Draining the oil found some filings and knew I was in trouble. Indeed I spun two rod bearings.

I've worked on many engines with a bottom end going out.....but this is the very first time it's sounded like that.....like your does.