Ok, as far as "Star Wars", Ben Burtt confirmed there were 3 different versions of the soundtrack for the original release. "One was a Dolby Stereo, for the 40 US theatres equipped for it at that time, one was a six-track 70mm version, and another was a conventional mono. Because you had to perform the mix over again for each one, you would do things differently, just by chance, and also by design." Even though the six track magnetic, and the 2 channel matrix for the Dolby System may have been created from the same base mix, that does not necessarily mean that they were identical.

So the appropriate way of recreating this would be to have 3 soundtrack choices on the DVD. One would be a Dolby Digital 4.1 soundtrack which would recreate the six track magnetic (the six track was 4 main channels, and 2 low frequency channels). The second soundtrack would be the Dolby Digital 2.0 Surround, to recreate the Dolby System optical tracks on 35mm stereo. The third soundtrack would the Dolby Digital 1.0, to recreate the sound from the monaural 35mm prints. DVD is well capable of having all these included.

My understanding is that there were also differences between the original release 70mm and 35mm versions of "The Empire Strikes Back," and not only in the soundtrack. I don't believe there were any of these variations in "Return of the Jedi."