This certainly looks a lot like an S&S34 (I own one), which incidentally was designed in 1968. Given your location I suspect you are well aware of this, but there is an S&S34 association down under that might be of help. They can be found at: Sparkman and Stephens 34 Association
Also, Sparkman & Stephens is usually pretty responsive if you have inquiries about old designs. They are located here in NYC and have helped me in the past with some historical questions.