i dont know,,, i know those guys would run two different plugs in each cylinder,, in front and rear,, they believed the g force had an effect on the fuel in the cylinder,, i cant remeber who it was,, but i know they ran autolites in the rear and another in the front, maybe ngk,, gapped the rear at like .012 and the front at like .018.. was either leong, head, hughes, prudhomme, bernstein, oswald.... one of those guys,,, back in the early 90's when i worked for a place where we ported their heads