1979 Dodge AVCO help

I checked the fuel tank and got the drain plug unscrewed and nothing came out. No water no rust nor fuel. it was bone dry. I put a little gasoline in the carb and it ran great. Tomorrow I am going to try to run it from a 5 gallon gas can. I can make a clunk weight and all that. I think it is fine and the engine sounded awesome. The motorhome is fiberglass and the walls are curved. I bet the walls are made of wood frame I don't know. I love the way it looks and I lost my vogue and this I like better. I don't know how it is built I would love to know. I can't find anywhere , where the walls are rotted to see inside the walls. It is a 1979 God only knows. My RTS bus has curved walls and it is all stainless steel tubing and plates It would be nice if this motorhome had steel framing in the walls.