Those heaters are diesel, that could be problematic. So you don't have electricity? I'm thinking a spare 8 D battery that you keep warm and charged in the house. Get an inverter big enough to run a block heater, put it on a timer to turn on the block heater a couple hours before you need to start. If you have to recharge the 8D, you should be able to run long jumpers into the house from the Ram battery. I recently lost my electricity for a week, but it only got down to -22F. I was able to run stuff in my house of an inverter on my Ram's battery (Yellow Top) . Unfortunately, my inverter would kick off when I ran the Ram, because it didn't like the Ram's 14.8-15 volt charging, so I had to run back and forth to keep my battery charged enough to start the truck. Last time we had -40F, I drove a Tacoma, it really hated to start. Had a Mazda car that broke the cam shaft off at -40. You might also put a warming blanket on the battery.
Inertia Spartan + cam, Circle D 3,000 stall ,Sonnax line pressure booster, MagHytec 68RE pan,and differential cover, Vararam, JBA's with cut outs, Rancho 9000's, Helwig rear sway bar,3:92's, extra rear leaf,Line-X Bedliner,GY Armortracs, 245,000 miles To Hell and back. 14.2/96 mph NEDW