There's a club in Victoria which I've always been meaning to contact. These are the contact details I have 'though they were noted in 2001.
Historic Motorcycle Racing Ass’n of Victoria Inc
8 Todd Lane
Romsey VIC 3434
Contact: David Large, Secretary
Telephone: (054) 29 6367
Fax: (054) 29 6367
I'm not sure what they do, or what records they may have, but they may be able to point you in the right direction.
Dave