In the UK an 80 series that was built for the UK market
should have front, center and rear diff locks, I'm to sure if it's the same for the Australian market, but I do know that
some of the JDM import 80's only had a LSD Limited Slip Rear Diff, no front diff lock.
As Firewout has said, "look for the diff lock switch" as it's an indicator as to if you have diff locks, without crawling under the car for a look see.
But beware, just because there is a diff lock switch fitted does not mean there are diff locks fitted to the diffs.
Have a look at this Youtube video.
I hope you have got them.
Good Luck.