I just picked up 6 Champion RC12YC from Advanced Auto. I ordered them yesterday, they stock them in their warehouse for next day delivery to the stores in metro Atlanta. The RC12YCC plugs are no longer available and the only difference is the "CC" means "Double Copper". Not sure what that means.

 

I tried to have Advance look up the RC12YCs so I could order them. They show them as no longer available. I will get them at Walmart or possibly Autozone. I don't know whey I am suddenly typing italics. I must have fat fingered something. Thanks.