What went wrong with the Gentoo Build? I've done a few rather quirky installations with x86 (on REALLY exotic hardware). I've also installed MkLinux on old powermacs. That was back before Al-Gore invented the internet. I may be a bit dated.
Truth be told, that is about the only distro for the PPC that will give you access to the latest software. Everybody else pretty much treats the Mac as the redheaded step-child.
Well except for Yellow Dog, they ONLY do PPC. For a good site with information about Linux on the PPC see http://www.penguinppc.org.