When I lived in Fairbanks, AK, we used an oil pan heater attached with silicon to the oil pan, one or two engine block heaters, and a heated battery pad. Many used a circulating coolant heater in place of engine block heaters.
Back then we would see ~2 weeks in a row where the temp never got above -30.
I wouldn't substitute an oil pan heater for an engine block heater - the engine block heater warms the coolant and the oil pan heater warms the oil.
Just another week until Winter solstice