Comment by Magic Marmalade:
Seeing my copy in daylight reveals that it has both the theatrical version and the special edition cut on the same disc...
(As per disc one of this issue -which is a win for me, as I wanted both versions :)
Having now ripped both in handbrake, the theatrical version comes in at 2 hours 18 minutes, and the special edition version at 2 hours and 43 minutes, which squares with what you said (163 minutes -as stated on my copy also), but I couldn't say where the extra 8 minutes you have cones from... Maybe extra credits for restoration/mastering, for new version?
(That's still a big gap though).
I did see that someone said the scene where the navy seal demonstrates the breathing liquid with the rat was to be cut for the new 4k version, as modern sensibilities would not allow it to pass censors - animal rights issues, and that if this was to be so, Cameron would not allow the release in UK, or something of that nature...
(I may be way off about that, as it was mentioned in passing on a video I saw on YouTube)
... So maybe that issue has been resolved?