Hi Breaming with bro, you're more likely to catch redfin or the odd Yellowbelly than to snag a Murray cod on your first go.
I mainly catch redfin down in Canberra and most of your bream lures will work on them. I've had the best success with a 2' pre-made swim shad in rainbow trout colour. It's only a cheapie Jarvis Walker lure from kmart, but has accounted for most of my catches. It also accounted for the one solid yellow I've caught.
I mostly use my 2-4kg graphite rod with a 2000 reel loaded with 8lb mainline and 10lb fluro leader. I've yet to even get a hit from something big enough to bust me off, but then again I'mbank fishing dams and haven't ventured out into the rivers.
Murray cod specialists generally use massive swimbait rods with 20lb mainline and up to 60lb leader as the murray cod can hit the metre plus mark.
Hope you get onto some though, they're on my list of fish to try and catch.
Like Dinodadog said, a 1/2oz spinner bait will work for the yellas and might get the cod interested. You can get the odd redfin on them too as they're not fussy when they're biting.