That terrific blog AWFUL LIBRARY BOOKS has a recent post on the bowdlerised edition of Fahrenheit 451 that persisted through much of the 1960s and 1970s - until Bradbury was alerted to it and insisted on his correct text being reinstated.Read all about it, with illustrations, here.
Bradbury later wrote a "coda" to Fahrenheit 451 in which he railed against petty (and not so petty) censorship.