Well, I've done it - I've managed to get all my old posts updated with new links to FLAC files of my uploads. In a few cases (mostly those for which I wanted to add text or picture files to the ZIPped folders), I've re-uploaded the original MP3 files, too, and provided new links for those. In at least one case (the Khatchaturian Masquerade Suite under Arthur Fiedler) I've added a cover scan which I wasn't able to do earlier.
I still have about 50 or 60 files on my Mediafire account containing uploads that I posted to RMCR (rec.music.classical.recordings) prior to establishing this blog, and my next project will be to upgrade these to FLAC files. Stay tuned!