Shortening the stems really cleans up the look of the back end. Now do you just want to shorten the stems, or do you want to lay down the license plate as well? Zmilin posted this gem a while back:

http://www.bonnevilleamerica.com/forums/...part=1&vc=1

I made one over a year ago using Z's instructions and it's super awesome! Cost under $25 including the price of the sheet metal, fasteners, rustoleum, and short stems from JP Cycle!