Although it's not a Sportster or Buell, it is a cool V-Twin. Check out this radical Moto Guzzi Griso, modified by Filippo Barbacane at Officine Rossopuro: http://www.officinerossopuro.it/
More info on this bike here: http://www.ipothesys.it/pag/home.asp
More info on this bike here: http://www.ipothesys.it/pag/home.asp