I applied for Victoria SS with a passport number and meanwhile I applied for renewal of my passport as well and obviously got a new passport number. Victoria granted me a SS with old number itself.
Later when I applied for 176 and when I notified Victoria of my TRN number I requested them to update mine, my wife's passport number include my son also as my dependent. They are happy to do that and confirmed me the same that they have updated and sent Form 1100 to DIAC.
So don't worry about your passport number. Go ahead with old passport itself.