If you're installing a cam this weekend....
 

read this:
https://ls1tech.com/forums/generation-iii-internal-engine/201761-attention-cure-ticking.html

Hmmm, I didn't install a new O-ring when I did my cam install. My car sounds fine, but I'll change out the O-ring with a new one when I go in to install my ported oil pump. In the pics you posted, it looks like the old one actually shrunk.