There are a lot of suppliers out there. You can find them in any car/truck magazine. Here are some of my favorites:

Red's Headers - CA http://www.reds-headers.com/
Sacramento Vintage Ford - CA http://www.vintage-ford.com/
Bob Drake - OR http://www.bobdrake.com/
Mac's Antique Auto Parts - NY http://macsautoparts.com/
Obsolete Ford Parts - OK http://www.ford-obsolete-parts.com/
Patrick's - AZ http://www.patricksantiquecars.com/
Hot Rod and Custom Supply - FL http://www.rodncustom.com/
Hot Rods Classic Truck Parts - OH http://hotrodstrucks.com/

Also, don't forget about your local NAPA store. They carry or can get most anything you need for your truck. Just have to find the right parts person willing to search. About the only thing I haven't been able to get there are the front brake drums. They were unique to 48-52 model trucks, and I got mine from Sacramento.

If you need help locating things, just ask. I don't need any extra parts at present, but thanks. Keep watching the various classified boards for parts wanted.