Sooooo give us some more info. Where do you plan on camping? What kinds of temps are you talking about? What is the mileage on you engine? I have cold soaked a 99 for over 24 hours at 25 below and it started, was not happy but it started and ran. I never worry even to 10-20 below because I make sure my engine/batteries are up to the task. If you want a backup get a Honda 2000 generator it will run at 30 below and do a fine job.
Early 1999 F350 AUTO 4x4 CC LB DRW 4.10 6.0 trans cooler, Front hitch, 2,000 hubs/ brakes, Bilstein shocks/steering stabilizer, Diesel site coolant filter 203 thermostat, EBV delete, new O-rings, new Oil cooler, RIFF RAFF FRX, Glow plug led, Pillar gauges, Lighted cupholder, Painless wiring fuze block, Harpoon/hutch mods, Removed axle blocks. Air bags, 5 wheel hitch, In bed 7 pin plug. Spare tire key delete. KLHANSEN on speed dial. 75,000 as of May 2019