I have not been able to find a vin decoder, a vin breakdown, or any information on specific VIN's for the willys.  I have linked the PDF and also the host website for the most complete information for production numbers for the entire willys productions range... 

Below are the links...

PDF

Willy's general info


http://www.willystech.com/faqs/WillysTruckFAQ.html
(the most comprehensive site i have found, covers restoration, specs, id, etc)

http://mvpimages.net/willys/show.htm
(sister site to above link)

http://www.kaiserwillys.com/
(second only to the above links for willys info)

http://www.public.asu.edu/~grover/willys/
(great source of information)

http://www.willysamerica.com/
(general info, restoration, parts)

http://www.off-road.com/jeep/willys/
(general info, restoration, parts)

http://www.willysonline.com/
(great gallery, forum, etc)

Willys Production Numbers


http://www.off-road.com/jeep/tech/history/serial.html
(most complete source available)