I explain it all in this post. It's a little different but strong and cheap as well as very rust resistant.
Explanation starts on the fourth post down. Let me know if you need any further info...
Spen?
or check the link attached
http://www.thecj2apage.com/forums/willys-trailer-or-not_topic12285.html
http://www.4-the-love-of-jeeps.com/1949-willys-jeep-utility-trailer.html