Thanks for taking the time to get those pictures and post them. I appreciate it very much.
The location appears to be the extravagant thermostat housing. Where your heating element is inserted. I have the securing black clip and bolt, just no heating element or cord.
Looking up inside the orifice on mine where the heating element would go, two to three inches back it appears to be blocked off. I'm betting at the factory there were two different castings on this part, one open for the heater, the other casing blocked off for those trucks without the heater.
There's a Ford part number on my casting BL3E-8A587-BB. Well not to sure this is a valid part number. I don't get any hits on this number online.
Online it appears BL3Z-8A586-B is the water pump housing. Can't validate if this part number is correct for trucks equipped with the block heater. Online I'm also seeing BL3Z-6A051-A for the heating element, and BL3Z-6B018-C for the cord.