AGSC-32C/ AGSF-32C Motorcraft. I think it depends on which GT40 heads you have. Actually the C or F appears to be the core material. Seems they're both the narrow plugs.
no he is saying to get the motorcraft plugs not autolite. I had those iron heads but i can't remember what i used to use. I'd try the ones he said. they are only about a buck.