The Vulcan 500 is a parallel twin and the 800 is a V-twin. The carbs
come off the rear of the cyl. on the 500 where as the 800 comes from between the cyl.
I can get a picture of the air box for you but I don't think it will work for you.
Send me a e-mail to
chfranklin@cfl.rr.com if you need the picture.