Wow! I just found this site and finally found that my 350L is not the only one in the world. I bought mine used about twenty years ago with a matching 4x12 bottom and haven't used it much because I haven't had much need for something this loud.
What are the pwer tubes you are using in your restoration? Mine hums so I'll have to look into the sugestion that someone had on replacing filter caps.
Thanks, T