I don't think a truck camper is the best thing for staying out in the extreme cold. You also shouldn't be out wandering around in -60F temps. One winter I worked on the ice roads up on the slope. They shut us down when it got past -30. A lot had to do it was too rough on the equipment. Steel gets brittle at real cold temps and starts breaking. We also let the equipment run 24/7. When we did have to turn things off during a phase 3 storm it took days getting everything running using Herman Nelson Heaters. Keep in mind during a phase 3 snow will pack everything solid full of snow. You have to shut your rig off as the engine will suck snow in it and will do damage. It takes a while to clean it all out.
We drive our pickup camper down to America in November and back in March. Don't think you can carry enough propane to stay out any amount of time in a camper. This year when we came down it was a little below zero. We kept the heater running while driving so our stuff wouldn't freeze (the camper was winterized). A tank of propane would only last 2 days. We used a Big Buddy heater when we stopped.
As someone mentioned propane doesn't work at -40........well unless you pour some gas on it and set the tank on fire. Used to do that to start my pickup when I would get back to the trail head after a trip in the back country. We used to use a couple sections of 4" stove pipe with an elbow at the end pointed at the oil pan and put a weed burner in the other end to heat up the engine so it would start. How do you plan on getting you vehicle started if you have to shut it down? What is the coldest you have started it after it sat for a while without plugging it in?
If you are serious about camping in those extremes get yourself an Arctic Oven Tent with a wood stove. You can stoke that stove to drive you out of it at -30. The add says -60, but....... I know when you get you far enough north there is no wood. We got a couple cases of those fire logs like you see in the grocery store. Doesn't take much to heat one of those tents.
https://www.airframesalaska.com/Arctic-Oven-Tents-s/2025.htm
Get yourself a Wiggy's Antarctic Sleeping bag and a reindeer hide for a sleeping pad. Nobody makes anything warmer to sleep in that I know of. I carry one when we head south.
https://www.wiggys.com/sleeping-bags/antarctic-mummy-style-sleeping-bag/
Just keep in mind if you get caught in a storm, you better be able to take care of yourself, cause it could be days before someone is able to help you out.
