Thank you Dave for photo help !
Here is a photo of the typical HYDRO FLAME furnace
They were used in truck campers, tent trailers and travel trailers.
I have found them for sale
for $20. to $80., I paid $40 on Craig's.....Of all I have found, none were working.
These furnaces are usually called "POT TYPE" or "GRAVITY TYPE".
You can see why they are called pot type by the 8" x 12" metal cylinder
fire box looking something like a pot.
Soon I will post photos of the modification process, stay tuned.
Doc the boonDOCer