This thread might be your best bet.

The way the releases seem to work. If you get one with a good audio mix, it has a terrible picture.

The latest release of GBU looks like somebody rubbed mustard on the lens.

The Mondo features better picture, but only in Italian.

Most recommend the German edition for the first 2 dollars films.

You could talk to TheHutt and kk650, as they have done a lot of work on GBU. Probably the best way to see the film, in my eyes.