good/best engine block heater?
KAT stick on pads, or similar = good
KIM HOTSTART = best (coolant thermosiphon).
No reason not to combine them; but some electrical knowledge about amp draw, etc, will be needed.
Search around on vehicle enthusiast forums, especially where trucks are used by utilities, mines, etc; a fleet mix of gas and diesel engines.
WEBASTO or ESPAR = full independence from utilities
.