Your question was about "warranty". If that "aftermarket" convertor fails for any reason, it will not be warrantied by Ford. If you have the repair done by Ford, with Ford parts, then the warranty for emission compliance as well as convertor hardware, are in fact covered. If you want / need to save a few bucks, then an aftermarket is fine. If this is an insurance deal, and I can find a dealer who will work on it, then I would go with Ford parts (my two cents).
__________________
|