I had modified the III-A to have octal sockets. It was missing the WD11 socket strips, and I figured trying to find them, along with the cost of tubes, wasn’t worth it. The set needed a lot of work. As it is right now, it can take 1A5 tubes (cheap!) and works well.
I can always go back and retrofit if I come across some extra strips some day, but in the meantime (since I’m not selling it or running a museum), I have a neat working mostly-original III-A.
I believe I got the adaptaters from Playthings of the Past.
Goog luck with the Majestic! It’s good the power supply works; I had to rebuild one in a Radiola 60 that took three transformers to supply all the various voltages and current draws.