Hier you find the first and surely best german-speaking forum for the 7 series BMW, moderated by my friend Herbert Posner and hosted by Emil Meyer:
Das 7er Forum (E32 und E38)
.
Emil Meyers BMW pages
(where the forum and a guestbook are located)
Herbert's BMW 7er Seiten
(Hi Herbert!)
For collectors of old radios: here you will find a very comprehensive database:
radiomuseum.org