The plot thickens... (no, not really)

the version this guy has sent me is higher quality because it's from an English THX-1138 (laserdisc maybe?).

Length is 81m36s

The beginning is in English and at some point it cuts into Italian (exactly after the off-screen narrator speech). This shows that someone took the audio (from the italian version that I have) and inserted it into a good-quality English video. This means there are no extended scenes, no "original" off-screen narration about Adam and no translated screens.

So this is basically the American laserdisc version with the Italian audio being re-cut to fit its shorter length (to further confirm this, some small portions of the audio are missing here and there, in these segments the audio switches back to English for a few seconds). This was quite common some years ago (at the time of emule and WinMX) when Italians ripped the audio from their sources and substituted it onto a good quality video source... so making a quick and good quality release