Use up all of your Florida diesel before getting to colder temps. Truck brought in some product for our plant in the middle of winter. Had BIG saddle tanks with lots of Florida diesel, came up to Ontario with a load and his fuel gelled. We helped him by taking him to get some additive and adding that and putting heaters around the truck. Eventually a wrecker took the truck to a repair place , drained all the gelled fuel and sold him some nice new "northern " fuel. Several hundred dollars and more than a day later he off loaded and went on his way.
All of this before I had a diesel truck. For what it is worth, the block heater cord on my 2006 was still curled up when I traded it in and I don't even know where the block heater cord is on the new truck! Always started fine in the cold.