I try to have it work the other way around whenever possible. The original remains the same and any remakes have their year added.
Though sometimes, it's better to state that a song is the original to avoid confusion. TMBG's "James K. Polk" springs to mind. www.madmusic.com/song_details.aspx?SongID=51370
What happened to this is a genuine annoyance. Someone overwrote the original mp3 with the remake, so I had to replace it & make a separate page for the 1996 version - calling the 1990 version from the 'Flood' album 'original'. Just to keep it from happening again.
The other aggravating thing is when original version mp3s are replaced with censored versions. Don't do that. This is supposed to be an accurate archive of comedy music & changing thing's for prudish convenience is right out. I'm sure many, if not all of the artists who make these tracks (& Wayne and myself) don't want these works censored on the song pages.
Leave the original as it is and do your own censoring if you feel an irrational need to censor songs on your shows. What's 'objectionable' changes throughout time and will invariably be ok in 20 years or so - just like pot will be legal everywhere someday.