Have you had any luck with those radio delete plugs for the doors/cab?
I have 2 of these on hand: 15965867 - Genuine GM PLUG, Side Door OpeningNo. The part number I found indicating the door harness plugs turned out to be the smaller generic door plugs for accessing the exterior handle bolts or similar. I might have one more option for looking up a part number, but not sure if that will have better results.
That looks like it's the right part in the images I can find. Do you have a picture of the actual part? I have a friend looking up some details on what might be a superseded part number of that.