Hi Charles,
Links to mail order vintage radio parts stores are www.tubesandmore.com and www.radiodaze.com. There are more, available on this web site under links.
Fear not about the inscription on the 6V6GT. Any old 6V6GT will do, as long as it is a good one. A 6V6G would work, but they are more expensive and not original to the set. 6F6 and 6K6 would even work in a pinch, too.
I expect you do not have a variac. If you do not I recommend you bring the radio up first without the rectifier, that would be a 5Y3, 6X5, 80, or 84 tube. First remove the tube then look underneath the chassis for signs of problems, such as mouse nests, or burnt or ruptured compnents. If the chassis is free of obvious nasties, turn it on with the rectifier removed. See if the tubes light up when the set is turned on, then check back to the forum.
The inscription on the vacuum tube looks suspiciously like a date code, indicating a 1939 model year. Look for numbers on the radio that start 62-???, 93WG-???, or 83WG-???. This will lead to the schematic.
Best Regards,
Bill Grimm