Canon has made a 10.5 scanner driver available for the 8800F
http://support-au.canon.com.au/contents/AU/EN/0100018002.html
However there does not appear to be a 10.5 driver for the 8000F. I could only find a driver that supports 10.4 and earlier
http://support-au.canon.com.au/contents/AU/EN/0900333601.html
This may work on 10.5, but since the web page states that it is PPC only, if you have an Intel-based Mac then this would stop it from working correctly (unless you forced your scanning application to open using Rosetta?)
Pahu