In fact all of Ball Breaker was originally written in 9/8 as homage to the Dave Brubeck Quartet – then later changed during the recording process.
Angus Young was quoted in The Wire magazine as saying:
Angus wrote:Yes, originally we composed the album in compound triple time as a tribute of sorts to Dave Brubeck and the whole 50’s west coast jazz scene. For a long time, as a group we felt indebted to their sense of experimentation and their desire to escape the boundaries of traditional musical forms. However we felt that ironically [laughs] the originality of the works suffered from this slavish to adherence metre…
The full interview is here - www.thewire.com/angusspeaks