Not sure. If you look closely at the roadshow LD, it appears more than one source was used. Added 70mm scenes are more faded and seem to suffer from more rainbowing.
And there is one scene in particular midway through Side 1 when two men are riding up on a horse that immediately follows a scene not present in the 35mm version. (I wish I could give you a screengrab or at least a rough timecode.) Not only is there a jump-cut in quality, but I think there was a slight shift in the screen composition, too.
My guess is the LD is already a composite of the 70mm and 35mm versions with higher-quality 35mm shots used wherever possible. If that's the case and the aspect was already altered to match one or the other, there might not be much of a difference between it and the DVD to contend with.