Enough of the back and forth stuff here, if you want to be at stock as can be with no questions on quality of parts and the best performance from said parts, buy the stock spark plugs.

AC Delco 41-101 Iridium plugs are the best plugs hands down. GM wouldnt put them in the cars if they didn't think that. They are good for 75-100k miles. Those AC Delco 7mm are stock replacements aswell and are the best quality for a stock vehicle, again GM decided they work great and they are proven to do so.