Frank,
Try Just Mustangs or Mustangs of Melbourne, both have real good quality cars, and freight from there to Sydney is about $700.
Otherwise, check out the NSW Mustang Owners Club (MOCA), they will have a display at the All Ford Day Eastern Creek this Sunday, many members will be in attendance, they may know of a club car for sale, and usually at the all ford day, there are cars on display for sale, so could be well worth a visit for you.
Cheers
Keith