Gents,
Thomas Muller wrote a very nice article about the 20 year anniversary of the E34S ///M5 in the latest issue (#151) of EWB. It (only) describes the HD9x versions, but is very comprehensive and includes the special models including the Winckelhock, Cecotto and Naghi variants. Well worth the read.
EWB is not availabe at your local bookstore. It can only be ordered directly from EWB.
More details:
http://www.edition-weiss-blau.de/BMW-selection, BMW-Buch.htm