Have you tried the Australia Archive
Website? This is an example of what I found. You can order the records from there and it may give you an idea of where your family came from in Italy.
Item details for: MT269/1, VIC/ITALY/MARESCA ROSA
MARESCA Rosa: Nationality - Italian: Date of Birth - 1863: First registered at Prahran
Contents date range
1916 - 1920
Click to see which government agency or person created this item.
Date of decision
14 May 2004
PAPER FILES AND DOCUMENTS (allocated at series level)
24 Feb 2004