Firstly let me say I'm no expert here, and being 40 years old I'm hoping some of the "older" guys might chime in...
Australian model would either be red or gold.
The K2 models unlike the u.s. we're sold here for a few years - not just '72. Up until '75 when the "sports" came out.
Two things that I know of that are different between the u.s. and Australian models.
The u.s. models have are a mph speedo and a buzzer that sounds when the Indicators are on, it's mounted behind the headlight and has its own cancel switch on the l.h. handlebar.
Thirdly will be the Compliance plate on the steering head, it should state ADR rules, if it says " this vehicle complies to federal laws etc" then it's a u.s. model.
Not a lot of info but hopes it helps, post some pictures of your bike it may help to identify it.
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