Thanks for the work & posting! Nice sample clip!
(My old-version MPC-HC player didn't like the FLAC audio. VLC played it fine, though.)
I looked around the other THX 1138 thread to find the multiple laserdisc-versions compare caps (US, UK, JP):
THX 1138 preservations (Italian Cut available, see 1st post)
http://originaltrilogy.com/forum/topic.cfm/THX-1138-preservations-Italian-Cut-available-see-1st-post/topic/11741/
Most of those pictures have disappeared as a result of Imageshack's recent site revamp.
I did find a page that still had some compares ..
http://originaltrilogy.com/forum/topic.cfm/THX-1138-preservations-Italian-Cut-available-see-1st-post/topic/11741/page/31/
.. but those were showing crop-differences (US & JP as a single capture as they were cropped that same).
As I remember, the JP brightness/contrast differed slightly from the other two.