Where's the core heater on a 93 7.3l Dually?

[93dually]

I have tried to locate the core heater on my 'new' 93 dually with a 7.3 liter engine. There is no plug wires that I can locate and I see no place on the block for a wiring harness/wire to plug into. Any help would be appreciated. It has been somewhat hard to start a few mornings when in the low 40's so far and since I'm in central Ohio, it will definately get colder.

[NCHornet]

Not sure on a 93 but on the 99+ it is right at the base of the oil filter.