The first charter 747s came along by early 1973 (Wardair and World Airways) and they were fully Y-seated on both decks.
Regarding beds on aircraft, these go way back in time. The DC-3 was originally designed as a sleeper aircraft, the Douglas Sleeper Transport, as described above. As soon as night flying became practical then beds, for what was still very much a "first class" clientele, were felt to be required. Prior to this long routes such as the Imperial Airways flying boats from Britain to Africa/Australia would stop overnight en-route and the passengers were put up in hotels each night.