They never made one at the factory, my education in medium duty trucks has been a crash course since I bought mine while on leave from Iraq. My truck frame, and engine were made by International, the body was made by Grumman Olson, the front beam is a Dana, the rear end is a Rockwell, and the tranny is an Allison. I ended up purchasing the stack of phone book sized shop manuals which has keep all repairs and Maintenance in order. Several companies up fitted these chassis with 4wd setups for forestry and municipal services. The parts are hard to come by and expensive. After much searching, the army deuce and a half parts are bolt on and easily found for reasonable prices. Most being new old stock or factory rebuilt. The box should be moved over to the International in the next month or so.