Those are good heater but two things to keep in mind. 1 they are fairly costly to run if ran more than a few hrs a week. 2. they pull a decent amount of amps so you need to make sure you have enough supply (reason I could not use a electric one)
Oh and Jason her garage being attached will allow a easy instulation of a natural gas one that will run off the house supply (matter fact I have one you can have cheap)
If you buy a K1 heater buy one of the newer ones with a thermostat. I bought a new one last year and it is SOOOOOO much better than plugging it in then off when it gets to hot then on 10 min later when it is cold then off...etc
Im in call every other weekend for the last year and a half till a good employees can be trained and VERY seldom do I not get called. So just know it could be worse