From what I've read, the Dolby Stereo mix was used for the 1985 CAV pan-and-scan laserdisc. I know there's a mono mix (taken from a 1977 bootleg tape) floating around somewhere; not sure about the 6-track. I've heard it was folded down to 2.0 Dolby Surround for 1993 Definitive/1995 Faces LDs. Others have said it was PCM.
From the research I've done, the 35mm stereo mix made it onto the 1985 Laserdisc and it has been captured. Also Moth3r has a recording of the mono mix that's higher quality than the bootleg but it's missing some parts so some guy is working on a restoration of it. As for the 70mm, well there is one version of it that is in stereo but the quality isn't that great. There is also a decent quality version of it but it's in mono.