Your rig, your risk. Towing overloaded won't make your truck explode or the sky fall. Lots of vehicles out there towing well above their weight limit, of all sizes, and the world hasn't ended.
More likely: Components will wear faster, even towing within specs does that. If damage occurs to a component and you try to get warranty on it, and they find out you tow overloaded, your warranty for that component is toast.
Less likely: You get in an accident because of equipment failure and injure someone, and you try to blame Ford. The investigation will turn up you were overloaded and you're toast.