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.