I'd guess the lifter bores are not parallel to the cam, looks as if one side of the lifter is biased and it's not travelling flat on the cam, so you have an unequal impact loading where the lash gets taken up, that's displacing a small amount of cam metal. All that said, I'd put it on the crank polisher and I'd bet it looks like new, Lord only knows some of the stuff racers have crammed back into blocks "for one more run." S/F....Ken M

I can’t remember the last time I saw lifter bores parallel to the cam.

I'm pretty sure you know he meant "perpendicular"

Aww come on - it was supposed to be funny.

Yeah, my brain was trying to pick between square and perpendicular and my hands typed parallel. The point remains. S/F....Ken M

My two thoughts on this.
One - how many passes were on the valve springs? Were they allowing the lifters to bounce/skid? I change valve springs every winter. It just seems like cheap insurance to me. My cam is not as aggressive though. 683/683 284/288@.050
Two - I run heavy oil and an additive. I use Lucas 20w50 and comp cams break in lube with every oil change. Maybe I am giving up hp and et by doing this, but I have been 9.45 @140 in NSS trim weighing 3585. Light weight oils just are not worth it to me.

Appears like the lifter wheels are concave/crowned causing a localized edge loading. The material transfer of the cam may be from both the lifter wheel and some cam combined. if the 'chamfer' cut on the wheel was done AFTER the face of the roller was ground this could create these conditions OR... Also, someone mentioned they have tried different lifters...it's LIKELY those different lifters use wheels from the same manufacturer.

We have seen this “wear” for years, in blocks with bushed lifter bores, and using quality oils back in the 70’s.

Thoughts back then were the lifters we’re rotating against the guide bars, valve spring issues, pushrod deflections.

Point remains, based on seeing this for that long, it’s nothing to get worried about.