The circulating 1500 watt heater is the Cadillac but if the engine is out, install a block heater on both sides if they'll clear. Just use one at a time, if one goes out, you still have the other. I lived in AK for 24 winters, I'm speaking from experience. It can't hurt to install a battery blanket either. If you have an automatic, get a pad heater for the tranny pan and while you're at it, a pad heater for the engine oil pan too. Don't plug in overnight either, get a timer or plug in a couple hours before you need to start it, saves electricity.