To update my post,
I was curious and dug deeper.
I have a 50,000 BTU ReddyHeater.
Still old as sin, but still works, been using it today without issue.
It heated up my 2 car garage, with only one insulated wall in under an hour to the point i didn't need a jacket, i use that to get it up to temp, and then i'm using a 30,000 - 80,000 BTU propane convection can to keep it at temp. only kicking on the reddyheater once in a while after i've been opening and closing the door to kick the temps back up.