The minimum rating would be 3700 pounds but it could be as high as 4600 pounds
In addition to the front and rear axle rating other items may affect the GVWR. Some of the items that could affect the GVWR would be the engine, transmission, differential, tires, wheels, brakes etc. Any of these items could reduce the GVWR. It's only as strong as the weakest component.
Here is a link to a site that will help decode the PC VINhttp://www.ford-trucks.com/forums/vindecoder.php
This is not an official Ford site but it will give you an idea of what is on your particular vehicle. It is important to note the disclaimer that this is a general description of the information generated by the entered vehicle's Vehicle Identification Number (VIN) and some pieces of data may be general to that specific model and not entirely accurate for the vehicle specified. If you look under the equipment tab it will give you the axle ratings. I would call the Ford Customer Service Group (800-392-3673) with your VIN and they can tell you the specific axle ratings for your particular vehicle.