I am trying to find information, passenger list, date of arrival of Toskan ship from Italy to Australia approximately 1956
I wasn't able to find mention of a ship called Toskan/Toscan, but there was a ship called the Toscano that sailed between Italy and Australia a number of times in 1956 (arrived in Australia in December 1955/January 1956, April and August/September). Unfortunately, not all of our passenger lists are indexed or digitised, and therefore, it is not possible to search online for individuals in your period of interest.
If you would like a copy of a passenger list, I suggest you submit an inquiry using the form at http://www.naa.gov.au/collection/forms/par-inquiry.aspx. A reference officer will search the records on your behalf.
If you are researching an individual/family who migrated to Australia, you may be interested in other kinds of immigration records in the National Archives collection, http://www.naa.gov.au/collection/fact-sheets/fs227.aspx. If you would like to investigate further, I suggest you submit a reference inquiry using the following online form http://www.naa.gov.au/collection/forms/imm-inquiry.aspx.