You may be correct if Ford now measures speed directly off wheels, like by using the ABS sensors or something similar. On older models they took speed off transmission shaft that measured driveshaft speed. In those cases changing the rear gear ratio required speedometer recalibration.
After thinking about this a bit: you do need to recalibrate the computer for the new gear ratio (and different rpm levels.). The computer won't be seeing the proper rpms for the speeds that it sees, and it WILL throw codes...
Good Sam Member 843599689
Current coach: Tiffin Wayfarer 24 BW
I chose not to make the change after all. I just did not have enough experience driving it to make a decision. I just set it up for towing but have not towed yet. It feels like I have enough power to do what is needed so regearing would not be needed. Also no one has said anything about already doing it and frankly I do not want to be the first. Technically I know it would work. Thanks for the comments.