Trying to exactly mimic his repertoire is not the answer. His knowledge of theory way exceeds yours, and no two people are exactly alike. My repertoire has overlap with S.Kasparov, Anand, Emms, Petrosian, etc, along with many others.
The other thing to keep in mind is that Botvinnik and Spassky were pretty much the pioneers of the concept of the "Universal Player". Pretty much every world champion after Spassky are all universal players, so there is no straight and narrow repertoire. As the following URL shows, he played the Nimzo-Indian as Black, he played the Grunfeld as Black, he played the King's Indian as Black, and those are just the things he played the most against 1.d4. He has played many other openings and defenses as well.
http://www.chessgames.com/perl/chessplayer?pid=19233
Does any one know what Bobby Fischer's opening repertoire was? I'm trying to play exactly how he did.