when i used xpostfacto on my 8600 (10.2), (please, if you try this, KEEP OS9 and do not raid the drives! if your back up battery is dead, you will be unable to boot your computer into an OS, and it is a pain to reinstall when it stops booting OSX and you forgot to check the box to install os9 drivers onto the hdds, i got frustrated and put my 8600 away for later) as far as i know, it was not an emulation. it acknowledged that the computer it was running on had a 604e cpu, not a G3 or G4. i think that xpostfacto simply disables the "locks" on the osx installer and when it boots up, and that it also installs drivers/kexts to support the older systems.
Anyway, good luck w/ your kanga, and let us know how it goes, i might try to put 10.2 or 10.1 on my hooper when i get more ram.