It looks like the guy who posted this clip on youtube, owns the same cut as you do, erri_wan. Maybe we should try to contact him? Maybe he have some info regarding this rare cut.

http://www.youtube.com/watch?v=4RTRKQkoQHg&feature=related

It's the ending of the film from an Italian version, which to my eyes looks very similar to your alternate opening clip in overall colors and contrast and it have Morris D. Erby titled as "Negro" in the credits, there's also a white cue mark visible at the end of the print.

On one hand I'm very excited and happy there's unique Donald Pleasence footage in this cut but on the other hand it makes it impossible to fully reconstruct this cut with widescreen footage from the Laserdisc.