I don't think a regular electric blanket would work. I don't think it generates enough heat directly to the engine. Those dipstick heaters
would keep the oil in the oil pan loose enough to flow easily but the mass of iron in the engine will stay cold. And it will keep the oil loose in the oil ports cold and congealed as well.

I had a friend in Alaska, Barrow or Fairbanks I think, who said they outlets in some of the parking meter like devices to plug a block heater in.

I think you'd need more direct heat. During the Korean war some trucks were kept warm with coal fires between garbage can lids slid under the engines. I can't verify that but i heard it from a vet.

Don