There is some misinformation in this thread.
Dot 5 is silicone based, not Dot 4. Dot 3 and Dot 4 brake fluids are both glycol based.
Don't use Dot 5 in your truck, use either Dot 3 (recommended) or Dot 4. The main difference between Dot 3 and Dot 4 brake fluids is that Dot 4 has higher wet and dry boiling points so it's better than Dot 3 for applications where the brake fluid can expect to get hot, such as on race cars. I think you'd be wasting your money using Dot 4 in your truck, assuming that you are driving it like 99.9% of F-150 owners. It won't hurt but isn't necessary.