BBK made an adapter setup called the Instacharger, quite simply enabling you to bolt an M90 onto a 5.0. I don't know how many were made, but it seems like they are quite rare. Right now BBK's website shows the Instacharger, but it's only available for Rangers. One might come on on eBay..you never know.
Keep in mind - there's A LOT of custom bracket and plumbing fabrication on that Eaton, and he's using a Haltech efi set up to manage things --- you're probably gonna be better off in the long run just looking for a used KB twin screw set up for the Fox if you want a positive displacment unit. Making the Eaton work, as you can see, is lots of work.
If you're gonna try to cobble together a used system inexpensively, you might be better off going turbo than supercharger.