Do any of them have a system partition on? The reason I ask is that because on some of the debug traces you've sent me, a filesystem has been identified on the Apple_Driver43_CD partition. Therefore there must be some other logic involved with Apple's Open Firmware in order for it to locate the partition containing the installer.
On a Mac-partitioned disk, there is no such thing as a "system partition" (that is a DOS thing).
Apple OF looks at the partition types (which are strings), and uses the first one that is "Apple_Boot", "Apple_HFS", or "DOS_FAT_", if you do not give a partition number (or partition # 0).
FWIW, it normally boots "hd:,\:tbxi" which means the disk with alias "hd", potentially some partition on that, in the blessed folder ("\"), the file with any creator and file type "tbxi" (which is a bootinfo file) (":tbxi").
I don't think you want to recreate all the logic (and lack of it!) behind how Macs boot.
Segher