There is some good news for those who used their ingenuity to install MacOS 8.5 on their PPC-upgraded 68K Macs. MacOS 8.5.1 should upgrade 8.5 on your system as-is, i.e. no tricks or hacks required.
I just applied the 8.5.1 upgrade to my P475/PPC601/100 Mac which was running 8.5. The installer ran without a glitch. This implies that the installer does not check the Gestalt mach id, only that you have 8.5 installed. It also implies that the installer does not touch the resource in the System file that was modified to get 8.5 to recognize PPC upgrades.
This is good news for those with PowerCards, PowerPros, Turbo 601s, Macintosh Processor Upgrades, and PowerBook 520/540 PPC upgrades.
For more info on the MacOS 8.5 hack that allows installation on "Unsupported" PPC upgrades, go to <http://members.aol.com/robertotec/mac/macos85hack.html>