I wonder that bad camshaft lobes could make such a sound. People on a classic Mopar site I visit often fail cam lobes during startup, due to high-lift cams w/ high spring pressures, plus the low-zinc oil today. Those failed lobes look much worse than yours, yet people report no significant noise. Of course, those cams ride down in the block (push-rods). I had a failed OHC once (Dodge 2.5L) when a drive service delivered the car cross-country w/ oil light on and 1 qt of oil left in the pan (did oil change & left drain plug loose, clueless driver). It made just a slight tapping sound, and the lobes were very worn. Indeed, the ridge you speak of appears to be in the axial direction. If true, that could be just normal wear from where the follower doesn't touch the lobe. The path the follower rides looks smooth.

As post 11, I had the vacuum pump follower bearing failure a year or so ago in my 1985 300D. My son only drove ~100 miles from when he heard the noise begin, but the follower arm was cut half thru by dragging on the roller-coaster. A little more and all that would have slid into the timing chain!!! I still had good vacuum, and couldn't pin-point the noise, but removed the pump to see. It was a tapping sound you could hear in the cabin.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans