I have a car port, so I cant help you there,...
However! Lately our whole base has been converting the aircraft hangar heating systems to radiant tube heaters. Basicly long tubes with reflectors above them, they have a natural gas burner every 30' or so and an exhaust fan at the end blows it outside. No interior ignition source so you dont have to worry about combustible fumes anyway. They dont heat the air, but the objects in the line of sight of the heater wich in turn heat the air. Works like a champ, can get the in several different sizes as well.
Here's a pretty decent sized one from Northern Tool:
http://www.northerntool.com/shop/tools/product_200455636_200455636

1956 GMC 370 dump " 'Tater "
1970 VW Volksrod "the Black Bomber"
2007 Chevy Avalanche
2020 Jeep Cherokee Trailhawk,
2005 Harley Davidson FLHTCUI

I dig all cars, old and new, whether they were hammered out of American iron, German steel, or Japanese tin cans. Being unable to appreciate them all is missing out on a world of great things.
But thats just MY opinion! :P