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I've run Jet Hot coated header's with very good result's. They claim the metallic-ceramic coating is slightlly flexible, and some street rodder's even use it on suspension spring's. You can buy coated header's directly from them, send in your old part's, of have the speed shop ship them there. Some guy's prefer to test fit new header's for possible tweak's, before having them coated. Recall a post here about a guy having a flaw in the coating, and Jet hot re-did it at no charge including round trip shipping.
Never heard of this company myself, but checking out their site, stuff look's pretty good. If you're looking for a custom application fit, probably couldn't go wrong with these guy's. Getting back to the original question, bought some coated header's from Summit Racing, and were shipped to me directly from Jet Hot. Probably the way this is done with most manufacturer's .