As I thought, the files are simple mp3 files that open in my Music section of iTunes. I assume they open for you in Books because you have altered them under Get Info-Options as I mentioned above. This works on your computer/iPod etc. but the info doesn't actually alter the files themselves.

One thing I do totally separate from amplificathon and the Archive is to compile podbooks for readers. I've gotten behind in doing this since normally I upload them directly to the Archive, which has not been possible lately. I'll be happy to make one for you asap, however, if you'd like.