[chiphead]

It's a '69 400 with the 11 bolt water pump and the later balancer.

Here's the results of today's testing:

Similar noise with both belts removed
Some belt and fan noise went away, making the rattling sound easier to hear. It sounds like sheetmetal contact/rattling/tapping near the center or front of engine.
All rocker arms adjusted and all pushrods spinning
Balancer is a nice SFI piece, not slipped or coming apart
Bottom pulley bolts are tight. RARE billet aluminum bottom pulley
I need to check balancer bolt with a socket, but the balancer didn't have any slack when I pushed/pulled on it.

On start, It doesn't make the noise for the first 15-30 seconds, then the noise starts. I stopped/started the engine 3 times, and there is a slight delay between engine start and the onset of the noise. Can hear it topside, loudest near the front. Can't hear it under the car, at least not over the exhaust. It almost sounds like the exhaust hitting something, that sort of rattley tink tink noise. But coming from inside the engine.

I pulled the fuel pump and used an inspection camera to get a few pics of the fuel pump eccentric. I used a screwdriver to move the outer ring to the front. It seems to have about .100 or so of forward/backward slack on the inner eccentric. The outer ring will sit flush against the gear or move forward as the pics show. Sorry for the weird angle, its hard to get in there and take pics.
Is this normal? I got a video too, but will have to upload it to YT later.