hey EZ if you know what an electric water heater element looks like thats what I got except its 12volt its 7 inches long with 1" pipe threads the only bad thing is it can burn out like a water heater element if its run dry. EZ for summer use your design should work great for winter though I don't know if thats still enough heat I don't know how efficient those heat exchangers and filters are but I bet that heat exchanger would probably be the best but anything more then probably 20% veggie your going to need heated fuel lines