Those plugs shown above are stock heat range 09+ 5.7 (Eagle). The Eagle heads use a gasket type plug, the 08 and older 5.7 don't use a gasket and have a bevel that seals the plug to the head.

A 1 step colder plug for an Eagle head (copper) is LFR6C-11 (NGK).

StricNine

79 Li'l Red Express, 15.04 @ 89.57
09 Challenger R/T, 11.95 @ 115.92