Hi Kati and Welcome to the world of molded fiberglass RV's
Rather that ask that here, I suggest having a talk with the FORD regional office and get their documentation as to the differences and incorporate those changes. They can provide an "As Built" listing for your version as well as the higher rated version, and I suspect that there might be more differences than just the axle
ratios. In any event, get something signed by Ford before making changes, and double check with your insurance agent and an Atty. about any liability issues these changes may incur.
There are any number of vehicle models that look the same and have the same drivelines, yet can have substantially different tow ratings.
Doing ones own "Fix Up" to change a published towing rating is a minefield that is littered with liability issues and occupied by hungry lawyers.
What exactly do you want to tow and is it listed in our Real World Weights listing here? Trailer Weights in the Real World