go to ebay and type in military heater and see what comes up. there is alot of military vehicle heaters NOS that run multifuel and put out alot. I have seen them from 20,000BTU to 60,000. The only issue is they are 24V, I am thinking of trying to rig one up and run off 12V? figured it would not put out as much or blow as hard but then again 20-60,000 BTU's is alot. they have built in fuel pumps, built in blower motors. I am going to try it anyway, mount it on outside and duct it into RTT, it will run off my 5 gallon jerry can of diesel.
R