From Hotstart's 'Tube channel.
Here's a good look at installation of a tank type circulation heater. It's done on an industrial engine, but the principles are the same:
Here's a video describing the differences between the thermosyphon systems and the forced circulation systems:
And here's a time lapse infra-red video showing the difference in how the two systems heat an engine (thermosyphon on the left and forced circulation on the right). Notice how evenly the forced system heats up: