Garage Heating

Just find a 60,000 to 80,000 btu mid efficient furnace, that a furnace company is swapping out, and hang it horizontally in your garage close to the roof and chimney.
Also if you haven't already pored the cement, I would suggest laying down some 2" foam insulation to help keep in the heat in the winter.

FYI (the overhead garage heaters like Tony used are probably the best way to go, unless you know a furnace guy. You are probably looking at around $1500.00 installed including venting)