Try Jim Carter Truck Parts at 1-800-336-1913 or this link
http://www.oldchevytrucks.com/cart/product.asp?prodid=ME1431&i=|brake|||49|

Their website is not the easiest to use, but lots of parts and you can always call them for more info. I bought Huck brake shoes for my 1949 GMC 3/4 ton through Jim Carter.