I've been looking through all of these photos and I think this one is the only photo that I can make a judgment as to its location. If that's the elephant house in the background then it must be relatively close to where the giraffes are kept today at the top of the zoo.
I had the same problem and was a little nervous that these photos weren't actually of Adelaide Zoo (despite the fact that in 1975, my parents would not have been at any other major zoo) ... until I saw the giraffe photo and recognised the elephant house.
So the giraffes are pretty much in the same spot I think - their yard has been changed somewhat though.
