http://www.LPPerformance.com
has been toying with this idea as well. they SCed a first gen pathy with an Eaton M90 SCer out of a SC ford thunderbird...BAD ***. (check under the pics and vids)
they don't have anything available as of yet, so the first company to come out with it should profit nicely.
I wouldn't use the eaton super charger that comes on the Xterra if I was doing it...I think it's a M60....they are weak and even with the underdrive pully only give you 10 lbs of boost....