Update - I installed the new AC Delco R45S spark plugs , and as Jerry said... no issues . I'll put a few miles on it and pull a couple plugs to see if there's any change in perceived sooty appearance problem.

52Carl - on the fast idle issue , I made sure the throttle cable wasn't interfering with the eyelet, put a couple drops of marvel mystery oil on the eyelet area, made sure throttle knob in the cab was fully pushed in. No problem with fast idle on my test drive. Not once.

So after all of the deep dives, overthinking, fixing what wasn't broke ....I think I'll just drive it.

Ron - - Dusty53
1954 Chevy 3604
In the Gallery Forum
"You can't dance with the Devil and then wonder why you're still in Hell."
"They will forget what you've said, and they will forget what you have done but they will never forget the way you made them feel."