What's the deal with champion?

Heat range is one of my beefs with Champion. They have been consolidating and consolidating and consolidating but without putting any improved engineering into their plugs for an actual wider heat range such that the jumps are huge between their heat range offerings. The NGK "5" heat range is smack on where it needs to be for a stock or kinda-stockish \6, 273, 318, 2.2, 2.5, 3.0, pretty much anything that specs a Champion 12, 13, or 14. The NGK "6" heat range (bigger number = colder plug in NGK) works well with high compression or forced induction. The best plug for stock/kinda-stockish slant-6 with pre-'75 head (with plug tubes) is the ZFR5N; read about it at the linked thread.

And yes, run the plugs and then read 'em!