I got my 04 air box in today, and there is quite a difference in the two years. If you look at the photo below, you can see the area where I'm pointing with the pencil is set back 3/4" more than the 03 air box. That is all the space I needed to get the boot to fit.
I went ahead and made a template from the ring that clamps the boot to the box adding a little bit around the outside to seal the airbox. I kept testing it and trimming where necessary:
I then cut it out of aluminum sheet I got at Lowe's, sealed it with gasket maker, and added sheet metal screws for security:
I ran out of time today. I'll fit it tomorrow and hopefully get this dude buttoned up and ready for a ride report.