this question is for you guys with supercharged engines,what brand of plug do you like and what heat range are you running.

NGK V8's

Non-projected tip NGK -9's.

only 2 guys know what plugs you use?

For a gasket style plug,forced or natural induction. I always try to use a NGK R5672A-8 this is either for alum. or cast iron heads. To use a non projected plug is going to shroud the spark in the combustion chamber. I believe; you need enough heat range on the ceramic to control plug fowling at idle, but not at off idle or higher rpms. A/F ratio needs to be correct in order to prevent fowling, detonation and pre ignition. This also pertains to compression ratio, timing, fuel octane # and what is the water temp when idling. If a piston dome interferes with the plug electrode you would either index it or use a non projected plug. I know in the past Merc used like a MR 43, I believe this was maybe due to fuel back then and now we are needing the engines to burn cleaner. Maybe a little to much info. Hope this helps.

Ngk br8

a/c 41t

But those were no where near the HP motors that I know your asking about !!!!!