You can run that off your inverter if you have one. One of my buddy's runs a 600 wat one of his inverter
A 300 watt heater in a truck? You might as well light 3 candies. If i wad in your shoes i would buy an espar unit. Yes it's expensive; but will pay for itself by january.
Well that's one way to get yourself a new truck. LOL Think I'll stop and get some hot links. You going to be near IA tonight Pete? Or should I just fire up my grill?