After several measurements using play-doh, at the top of the cover in four locations, the least distance is 3/8 inch in the center. I understand that 3/8 is typical for a stock 66 427 425 HP clearance. I am considering a 1/4 inch heat insulator gasket. That would then only allow 1/8 inch to hood clearance. I have tried a 2 1/2 inch air cleaner. With it, the top of the cover rest on the top of the carburetor which would create other problems. I do not want to make any modifications to the intake. Does anyone know of a 1/8 inch heat insulator gasket for my Holly 3247 carburetor or any other suggestions?