Keith's website has a lot of very good information including a copy of the 1947-53 Truck Shop Manual. Another resource that I found very useful is the 1947-54 Truck Factory Assembly Manual, which is available as a reproduction and can be purchased from several different vendors. Be advised though that all the drawings are 1954, but is still very helpful.
Another thing that I found very helpful while rebuilding my '50 were old brouchures, data books, etc that showed actual pictures of these old trucks. There are also a couple of other sites like this one with awesome forums with plenty of knowledgable folks who love to cuss and discuss. My regular hang-out is the Classic Parts 47-54 forum. Stovebolt Pages has a great forum too.
Links to both.
www.classicparts.com www.stovebolt.comGood luck, Ken