spar plug

[tubman]

If they are older Offenhauser heads, there may not be a direct fit plug available. There was a long discussion on here that came to the conclusion that a spacer will be required on the older Offy heads. Start with this thread : https://www.fordbarn.com/forum/showt...ht=offenhauser.

Also, it's probably not a good idea to get hung up on brand loyalty where spark plugs are concerned. Your "favorite brand" may not have a properly fitting plug available.