Try a TORX T-40 or 45
Actually, I changed the brakes on my wife's car yesterday and I can confirm that the tool you need is a 9MM Allen Wrench...Hard to find in Auto Parts stores since Ford doesn't want people messing around with the brakes (ABS.) No different than any other brake system.
9mm Allen wrench
Should be 10mm or 3/8ths Actually, it turned out to be 7mm Allen wrench.
7MM
7mm Allen wrench
To tighten and loosen Allen head bolts
7mm Allen
The caliper bolts can be accessed from the rear of the caliper. After removing the tire you can view the recessed brake caliper bolts. You will need a large Allen wrench, as these are Allen head bolts. Consult your auto parts store for the proper size Allen wrench. Common toolbox wrenches will be far too small. I would advise to spray down with some WD-40 the night before. You should also make available a large hammer to hit the wrench and loosen the bolts, as it is an akward position to muscle the bolt free with a short wrench.
it's a 3/8 wrench for both 2003 and 2004 caliper.
the front calipers take a 9 mil Allen head and the rear take a 7 mil, noth arent in your average homeowner Allen set
You need a 3/8 Allen Wrench
Most likely a 15mm wrench. Unlikely to be Allen in that vehicle.
I believe that is 7mm Allen key.