crap. erased what I was typing. okay, try again!
Ben, at -20 my old protege only needed 45 minutes to be warm, and 3 minutes of idle to be blowing hot air and melting snow/ice. at -40 it was more like 1.5 hours, and 5-8 minutes of idle to blow hot. Hopping in and driving after 1-2 minutes of idle left me hot after 3-5 minutes at -40. I was always toasty when I made it to school
I did have cardboard blocking 90% of the radiator, so that helped.
I think I had a 400W block heater, 250W oil pan heater, and a 1500W ceramic space heater in the passenger foot well. I didn't want to run it too long, it'd suck the power down! The space heater in the cab made the biggest difference in comfort.
15 (min) to 45 (max) minute block heatup, 1 minute fast idle, I drove away happy from +20 to -30. (colder than -40 is like a special hell we reserve other methods for).