Putting the finishing touches on my motor and wanted to get some opinions from you more experienced nitrous guys. My engine builder recommended I run NGK R5671A-8 gapped at .045 on motor and R5671A-9 gapped at .035 on spray. I noticed in the spark plug chart sticky it recommended a 10 or 11 heat range for spray. Details of motor and usage below and would like to hear your experiences and preferences.

Motor is a 394 CI solid roller set up for a 300 shot. AFR 210 heads worked over, 12.5:1 SCR, roughly 9:1 DCR. MSD manual timing retard. Shooting for ~500 RWHP on motor and run either a 200, 250, or 300 shot of spray.

It's not a trailer queen and I plan to put 3-5K miles a year on it plus some trips to the track. I'm sure I'll run into some stop light fun from time to time, so I don't want it to be a TOTAL dog without the bottle. Is there a range I should use all the time or 8 on the street, 9 at the track, or should I go with the guide and run even colder plugs?