What sparkplugs for GT40X heads?

Discussion in 'Classic Mustang Specific Tech' started by 1969mach1351, Nov 10, 2005.

  1. The plugs that came in my crate motor are AGSF 32C. Crossed to Autolite thats 104. Looking though a search everyone uses Autolite 3924. The difference in the plugs is that mine are tappered, have a .708 reach and a heat rating of D14. The 3924 uses a gasket, has a .75 reach and are a heat rating of D11. The main difference I'm worried about is the gasket/tappered. I heard alluminum heads needed a gasket, not a tapper??? What should I go with?