Well after proving on a dyno that the more you spend on a plug the more power you will LOSE , I lean towards the standard Champion RN12YC or RN14YC , use the colder plug , if you get any fouling move to the hotter plug , I would gap @ .040 if you have a high output coil , .035 if you have a std coil
You could also use Autolite plugs , not sure of the heat range / #s for those