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any suggestions on what i should use...the best plugs i can get would be preferred. thanks guys
 

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any suggestions on what i should use...the best plugs i can get would be preferred. thanks guys
Plain old copper ones (Motorcraft or Autolite) and depending on how much boost, one or two steps colder. Depends on what heads you have for the exact part number.
 

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I have GT-40X (X302) aluminum heads and 10-12 boost. I use Motorcraft AGSF-32C gapped at 035. That is the suggested plug for that head according to Ford. It is tapered, 14mm thread size, fully threaded, and has a reach of .708. According to the Autolite site, 104 is the equal Autolite.

Just babbaling here but this comes up a lot.
From what I've read and I might be wrong, the GT40 iron heads can take either a AWSF-32C (Autolite 764) which is not fully threaded or the fully threaded AGSF-32C. The plugs themselves are not the same but the GT40 iron can use either one. If the non fully threaded version was used in a X aluminum head, the non threaded part of the plug could contact the threads in the head before the tapered seat is seated. I think this is where the confusion that comes with what plug to use in the various versions of GT40 heads and different versions of heads on some 4.6L comes from.
 
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