So
@Muddy Bean for what’s it worth, I spent some time comparing part numbers between a 2015 Expedition and Navigator. The rear quarter panel, side supports, bumper cover support, and hitch are all the same part number between the two vehicles. Obviously, the taillights and the bumper cover are different. But I’d wager that physically, you could do the swap using a Navigator bumper cover and taillights. Wiring would be a different issue, but I can’t imagine it would be hard to make that part work. The Expedition already has a separate wire for the turn signal, you’d just have to match it to the input on the Navigator taillights.