Spark plug questions

After reading this thread, as well as others I figured "why not". I am gonna try these Autolite 64's that I keep hearing about. Ordered from Summit that night and just replaced the Champion RN 12YC plugs in my stockish 360 last night. The Champions had about 4000 miles on them, but like I said, for $1.97, why not. Idles smoother, and after 2 years with the old plugs I can definitely feel the change when I bury the right pedal. Kinda surprised me, but glad I tried 'em!