Mikey,
I don't know which plug would be best for your engine, but so far as how you plan to drive it will help determin the heat range. If it is going to be mostly street use, I woud stay with the called for heat range as the colder ranges tend to foul quicker in stop and go traffic. I can get away with two rangers colder when I was racing, but went back to the standard heat range for the street. Also if you are using an aftermarket ignition, Jacobs, MSD, etc, you will need to gap the plugs wider than normal to gain the optimum power.
Ron
