Hey , another Aussie here.
I think I can help with your problem.
Check your front and rear track width.(centre to centre of tyres)
The front should be wider than the rear otherwise the car will tramline.That is,follow ruts in the road,seem wandery,etc.
Most cars have the front track width roughly 1" wider than the rear.
With aftermarket rims it's pretty easy to get it wrong if you don't check this little detail 1st.
XA to XC Falcons (like the MadMax car for US readers
)and particularly hardtops were very susceptable to this problem.Because they had such huge rear guards you could fit massive rims under the rear and upset the front to rear track measurements.
Doesn't take long to check it out.