Recommended spark plug for eldebrock aluminum heads

The question on heat range is what is your compression ratio?!! I run champion and or autolite-no big diff

The compression ratio is somewhere between 10 to 1 and 9.8 to 1. The motor made a peak 509 ft-lbs @ 3900 and 430 hp @ 5300. Right now the plugs ngk heat range 7 seem to be a little too cold but I don't have any previous experience with aluminum heads. The carb used is a quick fuel SS- 650 which is probably small but it seems to work very well on both the street and at the strip.
Thanks for any advise
Dave