Spend your money on insulation. It will save you money by the end of the winter. Also do it right and get a LP or propane heater with a thermostat.
I don't own my house, the garage insulated walls(previous owner), I may do the ceiling this winter, and I heat it with a torpedo heater on diesel. Its real new, so there is not a fume problem. I also have a LP heater out of a house(read very old heater, you know the ones in your grandma's living room), I plan on hooking up too, and then not running the torpedo.
You'll find when you have a heated garage, you will do more work over the winter. Its easier to to maintence and mods.
Either that or buy a chainsaw, wood splitter, and a wood burning stove. It will heat you up 3 times, when you cut and load it, when you unload it, split it and stack it, and when you burn it. This is my least favorite form of heat. Very labor intensive. Might be good for you though, Mr Truck driver... .
Oh yeah, do your own R&D and report back later on how it turns out... ... . :-laf
Michael