Best guess on 416 motor

NGK, and somewhere around 6 for a street car with a big cam and no NO2. NGKs heat ranges are reversed... lower numbers are hotter plugs. Plus with some heat ranges you can get different hex sizes and extended or standard tip designs but you have to look a bit to find the right stock number for them. I use the SParkplugs.com website...lol. The BKR#E can be gotten from heat range 4-7, and with aluminum heads and moderate idle I want a hotter plug to stay clean. So something like BKR6E, stock #6962would be my first choice.