There is only one type of gas forge for the blacksmith. It is the kind that I have. I didn't invent it; Hans Peot did. Just today I compiled everything that I could about that forge and more gas forge stuff, including things about trying to design a better forge, even though there isn't any point to that at all. I even made up a bunch of stuff about propane in general, just to give y'all something to chew on. The following link will take you to that area of my website:
Pete Stanaitis