Upon cracking open the rocker cover, and attempting to isolate the area in the bank before doing so.. I found this on the cam lobe closest to where I thought I heard the bad lifter. (pictures attached). ll the lifters and rockers seem tight all the way through the cam rotation for every one. I can force a slight wiggle when the lobe is up on all of them. I'm thinking someone got in here prior to me and attempted to slap some new hardware in, albeit too late, and then decided to sell it. I don't know what could have made these marks. it doesn't cover where the roller on the rocker rolls (unless there is a slight crown). Could this small (picture exaggerates.. it's just barely perceptible and seems like it could be buffed out with an emery cloth) imperfection be the cause of all the racket (like a seriously lazy lifter)?

 

OK.. I guess picture attachments aren't working... I'll try linking them.

rocker
cam lobe

 

I would replace both.....

 

Sorry.. thought that would have been a given.. but you don't know my thoughts. :P

Before I just drop in new parts, I'd like to take some thought into what may have happened, and if I neglected finding the cause and going through this again.
I know low oil pressure, or oil contaminants, and/or a lifter might contribute to this, but the pattern isn't exactly what I'd expect.
There's a lot of hidden recent history, so the situations that might have caused it might not be here.. but I figured a discussion might weed out anything I neglected to check.