The fact that your F250 is older, the GVWR is lower than current models. Although new 250's realistically are between 7000-8000 lbs, they have ratings around 10,000 lbs and run rear axles rated at 9750 lbs.
Where you need to start is to research what running gear is in your truck and its ratings. Then get actual weights for your front and rear axles. This will give you an idea what you can haul per your door sticker what you can haul per your component ratings. If you go over your door sticker, you need to look at which component is holding back the capacity. Is it wheel, suspension, axle or frame (brakes will carry the same rating as the axle)?