Adding an inline block heater to a D4D with 3304

I've bought an in-line block heater for my D4D and am curious if the location of the current heater hoses is a good spot to put it? This cat had an enclosed cab with heater which I removed in favor of an open canopy and I had looped the hose temporarily.

My thought was to put my block heater inline with the existing hose as-is but the top port (#2) is on the radiator side of the thermostat which makes me wonder if I should instead go from 1 to 3 or 1 to 4 instead? What do you guys think?

[attachment=55309]D4D block heater lines.jpg[/attachment]

Thanks,
Jordan

I think you need to stay on the engine side of the thermostat.
The one on the front of the head seems like a good choice. The one midway along the head looks like it's into the intake manifold runner so air not coolant in that one I'm guessing.