Sam, try classicparts.com. They show a repro cap for a 3/4 ton, but they say 49 - 53. If you call, they might be willing to take some dimensions and check it out.
Also, there is one on ebay at
http://cgi.ebay.com/ebaymotors/ws/eB...K%3AMEWAX%3AIT
States 1954, but sure looks like it might fit.
Harry