I'm a big fan of cold weather camping, and my new (to me) 77 K5 will be perfect for this. One thing, however, is that it gets cold, and my blazer gets 6 mpg right now; as a result, running the heater is not an option for warmth. I'd like to install some sort of catalytic heater in the back, propane fueled. 1: are there any catalytic heaters designed to be installed in vehicles for such a purpose (auxilary heat)? 2: Am I going to need crazy safety devices to meet DOT standards? 3: Bad idea, good idea? Thanks in advance.