As it still may be some time until I can do a bit-perfect rip of this audio track, I can upload a decent capture for you of the Dolby 2.0 Surround, if you're eager to just hear the 70mm mix, I actually own a mint condition copy of this LD myself now. :) It's wave, in unedited form, split in two parts due to the side break, just let me know.
I had actually forgotten how jarring some of the music/sound editing was in some parts, from the moment when Nostromo is approaching the planet until they enter the atmosphere, the sound editing is surprisingly rough, it's actually hard to believe it was released this way, but I guess it was because of time constraints, the 70mm prints had to be out there day one.
But... many memories came back when I heard this track again, I owned a VHS copy of Alien released in Sweden in the late 80's or early 90's which I'm damned sure of had this same rough sound editing when Nostromo is approaching the planet, as I'm a little doubtful they utilized the 70mm mix for that old VHS release, I'm starting to wonder if this rough sound editing was part of the 35mm release as well.
Except, the few rough parts I mentioned, the 70mm mix is really great, good dynamic range with powerful bass content in various places, and it's very neat to hear all the subtle differences.
When I think about it again, I'm very doubtful the 70mm mix actually had split surround, the Dolby mix on Apocalypse Now is well known to be the first that utilized it, (it had been tested on Superman the year before) and Alien which was released the same year never gets any mention, Alien was in fact released before Apocalypse Now, which had only been screened at Cannes at that point. Btw here's a nice article on Alien 70mm openings: http://www.in70mm.com/news/2003/alien_in_70mm/index.htm