Around 2002 & 2003, Ford changed the way they mount their mirrors on the E-Series chassis doors.
They changed from a 3 bolt mounting pattern on the door where the mirror mounts to a 4 bolt mounting pattern.
The problem when ordering mirrors for the E-Series chassis is some 2002 chassis's that are supposed to have the 3 bolt pattern have the 4 bolt mounting pattern and vice versa with the 2003 chassis. The 2003 E-Series chassis that is supposed to have the 4 bolt mounting pattern has the 3 bolt pattern.
To truly know what the correct mirror replacement you would need, you'll need to take the door apart and take off the mirror and count how many mounting bolts you have.
After you figure out how many bolts you have on your mirror, you can email [email protected] a picture of your existing mirror and he will be able to identify what you need.