The mono and stereo mixes are important, since they are what most people would have heard back then, but the real prize would be the 70mm audio, which could be presented as a 4.1 mix with minimal remastering. With its innovative use of surround sound and superb dynamic range, not to mention the first ever use of separate LFE channels for enhanced bass response, it is the best sounding mix the film has ever had, and is entirely worthy of preservation. None of the other mixes can really compare to it, and it can be pretty much guaranteed that any subsequent remix would fail to capture its nuances and overall 'vibe'. With the original sounding so good already, there would be absolutely no point in doing so unless it was done very carefully and used the existing 70mm mix as its basis.

Strictly speaking I would want to see the film represented exactly as it was visually back then, but I'd be okay with having certain effects shots recomposited to eliminate highly visible errors and so forth.