I'm running a 468 with an 8-71 2 750 holley dp, solid roller and a pair of 345 AFR's. On the current set up it has 8-9 pounds of boost on 91 oct. The spark plugs I'm using is Autolite AR3931, and I think there a bit hot. When I look at the ground strap its like a brown color all the way to the base. What number should I change to that stays a standard type plug. Thanks in advance.