For Earthquake, the two LDs have the original Sensurround mix according to the LDDB forum. The initial pan n'scan has a stereo track that actually was the original transferred directly (so you can even hear the control tones present), and the later widescreen release simply converted the mix to Dolby Surround.

So the widescreen Superman LD has the 35mm Dolby Stereo mix without split surrounds?

As for Fox including audio, I think you're right GregK. I was recently looking into getting the corrected French Connection BD and it actually lists a mono track. (Which has never been released anywhere that I can confirm. It's always a stereo-ized version or multichannel remix.)

Another film that is never released with original audio is Bullitt. Every iteration is fake stereo or Dolby surround or 5.1. Every LD, DVD, BD and VHS that I know of. Plus the SE DVD and BD are missing a bit of leader inserted into the car chase.

Another one that I've wondered over is The Wild Bunch. The 5.1 restored mix isn't the most impressive and has always sounded somewhat tinny to my ears. I think because it was done for the early 90's restoration and was originally presented theatrically and on LD as Dolby Surround. Then it was taken to 5.1 for a later LD and the first DVD and simply ported for each new release. The BD is only at 640 kbp/s. I've thought about tracking down the mono mix on VHS and early LD.

Lastly, I'm considering tracking down the first releases of Godfather I and II with digital sound for the mono tracks in lossless. The restoration included them mercifully, but when upgrading to BD I found that they use the exact same lossy DD tracks as the DVD version!!! It's stuff like this that keeps Godfather and Taxi Driver from being definitive releases.