The Avco is a high end unit! But owning an old unit that has been neglected is not for the faint of heart. The 440 is an awesome power plant but has it's shortcomings. The Thermoquad carb is one of them. I would suggest you join a forum called Winnebago and Vintage MH's. Lots of Dodge chassis information. There are many parts on that engine chassis that are hard to find: Brake parts, thermostat, exhaust manifolds and more. DO NOT USE ETHER!!! You can check the fuel pump by removing a fuel line and see if fuel comes out. I am sure the carb is all gummed up. Easy to see if it has an electric pump by getting under and following the fuel line to the tank. If you can drain the old fuel or remove the tank for cleaning, do so. You have a lot of work to do!
Moisheh