Indeed the new 4K would have to be completely re-timed form scratch. However, even though it is less detailed the Mondo was from the Italian Leone family sponsored restoration, and merely making the adjustments for the International/US theatrical version would be possible, and then we could simply add the PCM LD mono track.
Anyone know where to find the Mondo anymore? I need a copy along with ordering the German BDs of the first two. According to bluray.com there is a new Italian BD but I don't know if it's the same master.
As for LD, the audio is the best for all three due to a lack of filtering that is found on all DVD/BD I have yet come across. On LD you have a far greater dynamic range compared to the lossy newer encodes. Especially noticeable in the score, sound effects and gunshots. These same transfers were re-utilized for DVD save for a few minor alterations. Fistful is slightly cleaner on the letterbox DVD but otherwise the same. FAFDM is slightly cut on the LD yet has some of the rare extensions like Indio's laugh. (essentially like MGM's battered 35mm print I saw, few extensions-no mention of Monco's name) The letterbox DVD is unedited but has none of the additional footage. GBU IIRC from one of our threads has a tiny shot missing on the first DVD, but otherwise the print for both letterboxed LDs and the DVD is the same. The original WS LD had Italian captions for the characters which matched that 35mm print recently on ebay. The remastered LD merely substituted the English captions and this carried over to the DVD.
EDIT: I will check my copies. I have the boxset and 1998 LD remaster, and R1 original DVD. IIRC the later LD's audio is a bit cleaner with less noise.
Seriously considering writing MGM/Fox/whoever I have to about their continued issues with the Leone films. Since hitting video they have been full of cuts, framing issues, audio problems, color fluctuations, damage, over-processing, improper "restoration", fake extended versions..does it end? The new DYS blu, if it ever gets released this year will probably look even worse than this, since MGM/Fox is content to mutilate it further with each release.
BTW, if and when that streets I have both WS LDs for correcting audio.