OK, first I'd like to know if I have well understood the situation...

The italian BD has the best color grading, according to many, while the new 4K version has a better definition, right?

Well, if the links I posted are to the right editions, there is a problem... the italian one is 167 minutes while the 4K is only 155 minutes... or is the latter length wrong?

I have also this laserdisc that should be 162 minutes plus additional deleted scenes in italian, perfect for the mono audio track.

I think for the video it's possible to color regrade the 4K version using the italian BD as reference, then use the latter for the (eventual) missing shots; for the audio, it is possible to use the laserdisc for almost all, then use the missing part from the 4K BD (if it has also the extended edition) or a previous extended edition DVD.

Well, I must confess I'm not well informed about the various versions of this movie, but indeed I'm curious to know if I could be able to help.

Also, this laserdisc box set could be indeed useful for the other two movies!