I live in the Yukon, regularly see temps past -40 C/F.
You need, at a minimum, all three heaters.
Get a block heater, a battery blanket and an oil pan heater. If you have a big vehicle with a large oil pan, get two oil pan heaters.
The standard rule of thumb up here is to leave it plugged in for an hour for every 5 degrees C past -25C.
i.e.
-25C leave it plugged in for an hour, then start and drive.
-30C 2 hours, then start and drive
-35C 3 hours
-40C 4 hours
Past -40C your vehicle will start and run, but you have to ask yourself if you really want it to. Even synthetic oil is like butter at that temp, so the damage you're doing to your engine is immense.
If you know it's going to be below about -30C for a while, block your radiator with a huge piece of cardboard or a tarp, otherwise your engine will never get up to temperature.
Also, drive very slowly for the first 5 minutes and don't turn your wheels to sharp angles.
Remember you don't have a heater on your trans or diff.. take it easy and let them warm up, drive very smoothly.
Have fun!
-Dan