06 Slvr Bullitt

This may be the wrong forum but I thought I'd ask anyway. Is there any way to retrofit a Shaker 500 6 disc mp3/cd head unit into a 2003 Mustang Ford that came with a 6 disc CD/non mp3 Mach system? I picked up a 2003 Ford Mustang through my dad's job last Friday and it has the Mach system. I really like a head unit with .mp3 capability but unfortunately there aren't any aftermarket in dash CD changers available. I have a Phatbox/Music Keg that I was going to install install in my '06 with a Kenwood in dash DVD headunit but I can get just about the same amount of music on the DMS catridge as I can spread out on 6 cds. Not sure if anyone has tried this but I wonder if it's possible.