Recommended spark plug for eldebrock aluminum heads

I have a 318 stroked to 390 with eldebrock aluminum heads and air gap intake. I am looking for a some suggestions on what spark plugs might work best. I usually race it once a week and drive it on the street to and from the track. I checked eldebrock site and they recommend champion ion rc12yc checking the heat range chart that seems to be at the hot end of the heat range. Currently I have ngk r5671a-8 v power racing plugs in there. They appear to be about in the center of the heat range. Just looking at them they seem a little to cold for the motor. I am looking for any ideas that you guys with more experience might have.
Thanks in advance
Dave