I've got an 03 night train and have a side mount plate. I got the bracket off of eBay ( http://www.ebay.com/itm/400532702123?redirect=mobile ). Looks great and easy to mount. All I did was pull the axle out and replaced one of the washers with this plate mount. I also bought 2 LEDs nuts and wires them so that the plate would have a light. Easy job as long as you are ok with removing the axle.
I got the DK Customs plate mount. There's a thick washer on the axle that the mount replaces just like JD said above. I ran one of their lighted LED bolts to it.