I'm very fond of the mono sound mix myself (duh!), having listened to the 'Story of' album countless times back in the day. My personal opinion is that all three sound mixes are "original" because they were all featured during the original theatrical run. But if you want to get technical, only the stereo prints (both 70mm and 35mm) were heard on opening day; the mono mix went into circulation the next month. So I don't think it's incorrect to consider only those to be original. I think it's really which version you remember best.

By the way, BrianM's 70mm recording has been posted to our favorite newsgroup.

Originally posted by: caligulathegod
Really neat from an historical perspective. Kind of a shame someone had to read the opening crawl.

I got a kick out of that myself. If you listen carefully, he is reading the crawl exactly as it is appearing on the screen and he pauses at the line breaks. The pauses match the line breaks in the pre-episode IV crawl. I thought that was great.