Jeff,
Thank you so much for that information

I will double check the model number of my "shell" and give Craig a call. I think I may need the control unit and the burner, but maybe they can source both. One way to find out
[Edited to say that I double-checked and mine is a GT6-3A; but I will still try the place you suggested.]
I definitely want to stick with the gravity type furnace, which is why I've been hunting for one. 1) No
electrical power needed; and 2) I'm a
light sleeper and a fan going on and off would wake me up each time.
Maybe I can make the hollow shell I bought into a real furnace
Raya