I mounted an 800 BTU catalytic propane heater in my Mini Shasta.
BUT as everyone has mentioned
NEVER LEAVE IT ON WHILE SLEEPING
I would light mine an hour or so before bed. Opening and shutting the door to get in would flush the cabin of CO2 and let in plenty of O2.
Then, once in the heater went OFF.
You can accomplish the same thing with a propane lantern using the same precautions.
In the right hand side of the photo is a shelf that slides in and out. My one single burner stove sat on that and could slide both outside into the galley and into the cabin.
On cold mornings I would slide the stove into the cabin and make a pot of coffee.
Once again,
NEVER WHILE SLEEPING
By the time the coffee was ready I'd have the windows open and the cabin was nice and warm.
Happy Trails
Len