I've been in the propane business now for 32 years. There's a reason unvented wall heaters are strictly forbidden in bedrooms and in my opinion, I would not recommend them period in any room unless it's for temporary heat.
The best heat for a well insulated, tight garage would be floor heat from a water heater or boiler. The problem is, it's very expensive, recovery is slow if you open your doors alot and most of us already have our floors in place.
Next would be, as Lefty71 said would be the overhead tube heat. And also as Lefty said, you have to have the ceiling height. It's economical to run, quiet and it's sealed, so it's safe with chemicals such as paint. Recovery time is quick too. It penetrates into everything in your garage including your floor so it gives a nice toasty feel. But, it will melt the vinyl top right off your car if your ceiling is too low.
That leaves either a hanging VENTED unit heater hung in one corner aimed at the opposite corner which is what I have. The problem is, they are noisy and not as efficient and in my garage (which is a converted corn crib), the heat never makes it to the floor. I freeze on my creeper! Or, you could install a high efficient house furnace and be creative with some ductwork and plenums.
Woodburners are great too if you have time for all the work involved and have access to firewood. There's nothing like wood heat and it smells great outside!
Whatever you install, National codes require the burner of any appliance in a garage to be at least 16" off the floor.
Or.... we could all take our muscle cars and move south!