* Driving conditions: City driving yields much lower MPG than highway driving. Terrain (hills, mountains) also plays a large role.
* Vehicle condition: Proper maintenance (tune-up, tire pressure) greatly affects fuel efficiency.
* Driver habits: Aggressive acceleration and braking significantly reduce MPG.
* Payload and towing: Hauling heavy loads drastically reduces fuel economy.
While you won't find a precise EPA number, you can expect significantly lower than 20 MPG, and likely closer to the low teens MPG, especially in combined city/highway driving. Expect even lower numbers if you frequently tow or drive in challenging conditions. To find information from other owners who have driven this specific truck under similar conditions to yours would be the best approach. You might find this type of information in online forums dedicated to classic Ford trucks.