DO NOT NOT NOT use the NGK IRIDIUM IN A COSSIE ENGINE over 300BHP...
Im leaving to eat so dont have time to explain and ive had long technical arguments with NGK Racing department over this and they finally agreed they were wrong and that catalogied number is NOT suitable, but i wanted to make time to tell you tell you this as i respect your many miles away and have only brief access to pick up your info Jim and i didnt want to read you bought 1000sets!!

The Plug you want to buy is the old R7234-9 or R7235-9.