It isn't possible to have a "left over 4R100."

When the 2005 model year started the plant had all the parts to install 5R110 transmissions. If they managed to throw a 4R100 in there when they were putting the truck together the driveshaft would be too short to reach the trans, the trans would be too short to reach the crossmember, and the wiring harness wouldn't plug into the trans. How would it drive off the end of the line? And that doesn't even consider that building a 2005 with a 4R100 transmission wasn't federally certified for sale, so that's a MAJOR fine for Ford Motor Company if it were sold.

Look on the blue data tag in the driver's door opening. Under TR there is a code letter. What is it? Also, what is the 10th digit of the VIN?