Ford wont warranty any part that doesnt come from them. any after market part found on a vehicle still with its factory warranty can even sometimes void the warranty there after.
Really you would have to consult a dealer on exact details. Typically they are very strict on what can and can't be modified. They would know exactly what you could do.
The normal warranty for Ford parts would be 6 months to 1 year. It depends on what type of part it may be and when you are purchasing the particular part.
