Check this company out. They have been around for years. They have engine warmers and cowl blankets.
http://www.tanisaircraft.com/index.html You can also build a heater using a kerosene fired space heater, the kind that look like this one: http://www.reddyheat.com/ get the local HVAC shop to build you a " Y " for the end of the heater and then install 2 scat tubes to stick into the cowl or up from the bottom or other opening. You can melt parts if you are not careful, so you will have to stay with this setup. And the heaters don't have to be 70k btu to heat your engine, you can use smaller ones that are less output and less expensive. With enough scat you can heat the engine and the cockpit at the same time.
