You may have a block heater, but no cord connected to it.
Or you may have a block heater AND cord. Look under the driver's side of the front bumper. The cord is probably tied up under there.
Here's a pic of where your block heater would be. Mounted in the oil filter housing on the front of the oil cooler.
If you really don't have a block heater there, but just a plug, let us know and we can get you the PN. You'll have to drain the coolant to install one.

 

The block heater should be there right above the oil filter, but being a California truck it quite likely didn't come with a cord. From what I remember all the 7.3 engines came with at least the heater element.

You should be able to pick up a cord at a NAPA store. The Ford part number is F4TZ-6B018-B If someone removed it a plugged the hole here is the part number from Ford for just the heater element F4TZ-6A051-A

 

Here is a pic of what im working with. Got a bolt where it should be.

 

Interesting that it didn't have a heater installed. That's unusual. The original purchaser probably had to pay extra for a "heater delete option" . Either that or someone removed it.
The PN that Bugman posted should get you fixed up. I'm sure it crosses over to a Hotstart or other Mfr part no. It's a 1000W heater.
on edit: Yep, a Hotstart PN DD8L-101 fits. Here's their catalog (see page43 - cords are on pg 48). Probably cheaper than from Ford.
Here's another option Search Amazon for "Zerostart 3500043 Engine Block Heater". Includes heater and cord for ~$50

 

Thank you for the advice and narrowing down mass amount of options

 

I just looked at a couple other sources Diesel O Rings and Riffraft Diesel and they both carry the heater and cord.

As for cost for the Ford one they are around $35 for the element and $80 for the cord on the low end

 

Sort of on topic here: A friend bought a Jeep Cherokee Diesel, a year or so ago, and when it wouldn't start last winter, he got it towed to the dealership (warrranty). They told him he needed to buy a cord for the block heater for $100. He said, no, you need to give me one if it's got a block heater and I need to plug it in to get it started in the winter. When the dealer's guy insisted he had to pay for it, my friend said OK, I'll just have you tow it here under warranty every time it won't start. The dealer's guy thought for a moment and handed him a cord.

 

I don't know why they made it a option in 97, all the other years of the OBS trucks got the heater and cord. Then Ford started to only put the cord on trucks that were in the cold weather package areas.

Dang bean counters.