First, join the Studebaker Drivers Club athttp://www.studebakerdriversclub.com. For the price of membership, you get the monthly magazine "Turning Wheels" with many articles about Studebaker cars and trucks, as well as ads from many of the vendors.
Then go to the web site that has a very complete list of Studebaker parts vendors:
Pick one or two of the vendors and develop a personal relationship via visits, phone calls, or attending Studebaker parts swap meets and club meets. You'll get better attention and help in your quest for information and parts.
Buy the reprints of the Parts Catalog and the Shop Manual for the M-series trucks from one of the vendors. Also buy the Shop Manual for the later 2R series trucks because it has more writing and pictures and describes the same parts and repairs much better. These books don't cost very much and will save you time and money during a restoration.