What kind of Spark plugs should I put in my 5.7L hemi?

OEM unless you have heavily modified the engine and need a cooler/hotter plug. When it comes to things like plugs, there will be no difference in the buttdyno no matter how much you spend, go for reliability.

I'd put in a good quality platinum plug, being sure to use anti seize compounds on the threads. Iridium plugs are not worth the extra expense and may actually last TOO long, especially in some aluminum head engines. Aluminum head engines may have the spark plug holes stripped when removing plugs that have been left in the engine for several years leading to a big repair nightmare. You are better off with with a good platinum plug changed every 40-50,000 miles. Iridium and other gimmick plugs will not buy you any performance increase over a platinum plug in good condition and cost several times more.

They are a JOKE! The BEST plugs are DENSO and BOSCH iridium plugs and NGK LASER plugs! They ALL have fine wire IRIDIUM electrodes! Denso also has TWIN TIP Plugs with TITANIUM On them! These REACT CHEMICALLY with modern fuel and burn MORE fuel MORE completely and yield the BEST ECONOMY and POWER from EACH and every stroke! E3 plugs come from CHAMPION and are interesting but do NOT have PLATINUM or IRIDIUM on them as far as I know! They do NOT react with fuel! BOSCH FUSION plugs are ALSO tremendous! expect 20% improvements in POWER and ECONOMY with them! BYE NOW!