While the illustrations may not be the best, this vision of Sydney's skyline in 1975 was published in the October 3, 1972 edition of The Daily Telegraph.
While the buildings featured were generally built (bar two or three), they were completed well after 1975. I have listed the completion dates of some of the buildings below:
MLC Tower (11) - 1977
Sydney Tower (7) - 1981
AMP Centre (18) - 1976
Law Courts Building (16) - 1977
Qantas Centre (5) - 1982
Gateway Tower (14) - 1989