I'm going to put my $0.02 worth in on doing it "on the cheap."
I'd either put in some curved tipped ceiling fans to blow whatever heat you do use back down, or put some cheap cover for a ceiling up on the bottom of the rafters to get or keep the heat lower. Either plastic or some thin luan wood panels will work.
For heat, if this is an option, go buy a Double Barrel heater kit,
http://www.northerntool.com/shop/to...e-fireplace-accessories+barrel-stove-supplies
Put it OUTSIDE inside sealed metal air box with the front open to the outside so you can feed it. then run you a couple of metal ducts into it from the shop with blower fan here, and then two metal ducts going back into the shop.
It'll get the chill off the place. A buddy of mine's parents let us close in the single car carport to use as a shop. We built one like this with a 30 gallon barrel inside a 55 gallon barrel with a 6 inch in/outlet. We had to leave the garage door cracked or we couldn't work it would get so hot in there. We used an "old school" 12V truck dash fan for the blower with no thermostat.
I worked at Ryder at the time and would save the old LuberFiner oil by-pass filters, cut them open and take the oil soaked filter media (wood chips) out and wrap it into baseball size balls inside heavy duty aluminum foil for fuel. We'd pick up all the pine cones at his house, get a fire started and toss one of these in to burn.
BTW, I remodeled your shop so the floor is down....