I was able to locate it the PT5/6 combo installer via waybackmachine. The very first revision original has yet to be located, but in my research this issue started with the Anthology II update anyways. I believe it does work in OS9 if you have a Pro Tools HD Core/Process card combo (I have loads of Accel cards and no Process cards in all my chassis).
My solution wound up building a Mac G5 – Pro Tools HD Combo with a 64 Bit PCI-X Expansion Chassis. Anthology II working great on Pro Tools 6-8. I may at some point test my theory about Pro Tools 5.3.1 HD and OS9.
