Spider webs tend to block up those old camper furnaces bad if they are not used or cleaned regularly. I agree for the time and effort to remove and install a camper furnace in a deer stand a portable heater with a CO safety shut off seems much easier.
Also lately its not been that cold in deer season. Couple opening days I wished for an AC unit instead of a heater.
My first camper (late 1960's) had a propane heater that had no circulation fan. The pilot was manually lit and turned off. It worked strictly by the "heat rises" principal and did a good job in a 19 ft camper. It also had a propane mantel light mounted on the wall. That thing threw a lot of heat just by itself.