What's the deal with champion?

E3 and all other "magic" spark plugs are a waste of money at best.
Champion quality has been going down fast for years; I long ago quit using them.
Autolites are now Chinese-made trash.

Go NGK all the way, and not the one in the book for your slant-6. See tune-up parts and technique suggestions, including spark plugs, in this thread. Remember to remove the metal ring washers before you install the plugs!