The V10's cat is $$$$ simply because of the the amount of platinum in it. That's why Ford replacements are pricey.
BTW - even though that particular P/N was discontinued, it really just means an updated part replaced it. You can install a cat from a newer V10. Of course, they are still $$$$. Most aftermarket cats don't have near the flow of the stock cat. But maybe some of the "high-flow" version do. Unfortunately I'm not aware of any independent testing. Best bet may actually be trying to find somebody parting out a V10 on craigslist.
