Another buggered 5.1 remix I forgot to mention: Grease.

When the film was remixed in 5.1 for the 20th anniversary re-release, they completely overhauled the music mixing to sound more "modern." You can read a whole lot more about it here: http://www.hometheaterforum.com/t/287394/a-few-words-about-grease-in-blu-ray

Here's the original mix of "You're the One That I Want" from an old TBS broadcast. And here's the remix. Notice the extra "It's electrifying!", the much louder background vocals and brass, and how during the second verse, the male backup singers are actually out of sync!

There really needs to be a preservation of the original version. Just take the Blu-ray, synch it with the original Dolby Stereo from one of the pre-1998 laserdiscs, and restore the original Paramount logos at the beginning and end from another film on Blu-ray (like Star Trek: The Motion Picture).

Chuck Pennington says that the original analog stereo laserdisc didn't sound very good, but LDDB says that there was a re-release of the full-screen LD with digital sound. They also list a Japanese LD with a digital track. Those would probably be the best source for such a project.