The last B-52 made was in 1962. The ones left flying all all the last B-52H variant, though NASA had a B-52B operational until about 10 years ago.
Many 747-100's were converted into freighters and I assume some are still flying. There were several flying in Iran for a while, but not sure of their current status. GE uses one as a testbed for engines that's very much still active, and it was one of the first ones flying in 1970. There may not be any left in regular passenger service though.