Go to the KnifeEdge forums website:

http://knifeedge.com/forums/index.ph...80bf4809c0a21&

Click on the G5 line and find the G5 migration tool - a sticky near the top of the page. With this tool I was able to get all my models, custom also, and sceneries, etc., just about everything from my G4.5 installation right into my G5 upgrade. Easy to use and it worked.

Not sure if this works with anything back before G4/4.5, but it sure was helpful for me.