[Jrainman]

all good choices here and Orge 90% efficency furnance is most likly a good choice because he only paid 300 for it ,and being 90% furnance it has a sealed combustion chamber so its a very safe option as well

The modine options are well suited for garages because they hang and dont use your floor space ,and if placed in the perfect location you can create a heat curtain so when you open your garage door a very min amount of cold air will enter .

Most if not all hot air furnaces will be optioned for Propane use as long as offer a propane conversion kit.

as also stated insulation is you best friend when trying to heat a space ,so opt on doing at least some insulation for better performance and economy.

There is another option if your are looking for big savings , because you live in a Coal region ,that means you can obtain coal at a very reasonable rate , they do make coal hot air furnace , they come very efficent also seal chamber and highly optioned these days ,you might want to educate your self on coal just because you live in coal region as I do and heat with coal including my house . its not what you imagine Days of heating with coal are very advanced .

And the most important reason is my heating money does not go to some other country or state ,it pays the local miner who mined for it, the coal breaker to process it and the trucker driver who delivers it to my home .