I have:
. Canberra 2001 by Roman Mika
. Melbourne 1999-2004 by Belini
. Phillip Island 2002 by Matthew Burge
. Eastern Creek 2004 by Marino Cervini
. Adelaide (Street) 2001 by Paul Schiller
. Bathurst 2000 by Glenn Durden
. Amaroo Park 2004 by dylan
The first 6 tracks above are good. I have Amaroo Park in slot 7, but it doesn't work for me. There may be other tracks out there somewhere.
These tracks are for GP3. No one has made a track editor for GP4.
Sorry, I haven't tried GP3 track editing/converting yet.
Good luck!