So it appears everyone's database is wrong on our alternator pulley (most everyone says it's a Motorcraft GP-720 which is obviously wrong when you compare them)

I've got the correct pulley here and the casting marks say "XL3U- -AA" Can anyone tell me how to figure out a part number from that?

I'm at my wits end and about to buy an alternator just to get this over with.

Coldie