Update:

He found that there is a different part number for the 2003 year model. My VIN was build September of 2003 so it may still use the older part number (left-over parts). Unfortunately I forgot to specify which line to him, so he's going to call GM tomorrow with my VIN and the part number and they're going to help him clear it up.

If nothing else he said he'd send me the 2003 version and see if it works.