[Elusive Part Number]

Are these what you are looking for?  Looks like they might go all the way from front to back.  The second piece maybe something they added after installing the light bar and cutting the factory piece.  

 

HC3Z2651728AD

https://parts.ford.com/shop/en/us/body/other-body-related-parts-general/roof-molding-roof-side-trim-molding-right-p-hc3z2651728ad?pdp=y

HC3Z2651729AC

https://parts.ford.com/shop/en/us/body/other-body-related-parts-general/roof-molding-roof-side-trim-molding-left-p-hc3z2651729ac?pdp=y

[Adding Brake controller to class IV tow Pkg]

It was very similar on my 2015.  The harness was attached to the back of the little storage bin.  I removed the bin, plugged the harness in to the controller, and clipped it back in place.  Then I had to have it activated.  I took it to a local shop and they did it for a fee.  Cheaper than what the Ford dealer was going to charge.  They wanted to charge one hour minimum.  

 

Some of the Ford dealers on Ebay who sell them you can send them your VIN and they will verify which controller.  I used forums like www.F150forum.com to figure it out.  Quite a few people on there doing the same thing.

 

This is for the Ford factory controller.  I didn't look in to aftermarket, but that may be what that short wiring harness is for.

[XTR Package and Antimatter Blue]

In looking at the MY22 order guide, Antimatter is available on XLT/XLT Chrome Package.  It is not available on the XLT Sport/Black appearance packages.

 

[Kentucky Truck Plant Question]

It was awhile back, but the last time I got to go through the plant they had two final assembly lines.  One line ran Expedition, Navigator, and certain configurations of Super Duty.  The other line ran Super Duty only.  I didn't see the body/paint area so I don't know about that.

[Tried to buy an Aviator (w/o success!)]

Have you looked in to a controller like the Curt Echo Wireless Trailer Brake Controller?  I don't know for sure if it will work on an Aviator, but it could be more likely to as it plugs in to the 7-pin connector instead of being wired in to the dash wiring harness.

[External Radio Antenna]

Ford has a shorter mast (16") they use on export F150 and F250.  Not sure if you can get it in the U.S. as a service part.  

 

Ford part number LC3T-18828-AC