Tapered seat spark plugs in an application intended for gasketed plugs do not dissipate heat properly. They will burn out very quickly, and the overheated plug tips might cause detonation in the combustion chamber that will blow holes in the pistons. Original equipment "AC" plugs are not the same as "AC-Delco" which is a product made offshore- - - -not from the USA. I'd recommend an equivalent heat range plug from Champion, Bosch, or maybe NGK if you can find something other than AC-Delco in the proper gasket design and heat range.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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