Damn, I want to find PS2 discs of GTA VC and GTA SA with the cut music, but no luck so far. As we know, these versions do exist, but I have no idea how to find the right retail copy. 
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I don't think packaging stuff are helpful for discovering cut music. But I've got an idea, We all know that R* uses in-game soundtracks for trailers. Check if there is any unused soundtracks. (used for game trailer but not for the actual game)
Honestly, I am not interesting in music, which was cut during the development. I just don't find it interesting.