There is a list of differences between the 35mm and 70mm versions of Empire, but since there are no recordings available, I find myself a bit sceptical that all of those are actually from the 70mm soundtrack at all. Remember, it was produced first, with some effects shots incomplete compared to the later 35mm release--so how does it make sense for it to have a more complete soundtrack with additional dialogue and more polished music edits? That doesn't seem logical to me. Some of those differences may be authentic, but some could well be apocryphal.