It sounds like you can swap the freehub but I'm not sure if the one you've linked to is what you need. See this thread here for some possibly helpful info: http://forums.roadbikereview.com/whe...al-181238.html

Note that the freehub pictured has a hex-shaped protrusion at the rear versus the threaded bit on the ebay freehub. Perhaps that hex protrusion is just a nut that you already have inside of your rear hub though.

You may have luck contacting Formula directly too: http://www.formulahubs.com/en/main/