There's an updated version of Extensions Overload available now.
Version 5.9.1 is fully compatible with Mac OS 9.2.1. The application is an extensions, control panels, control strip and contextual-menu management application. It contains details of 5,200 of these items, and lets users activate and deactivate them.
The application works with with all Mac OSs from System 7 to OS 9.2.1. It costs $29 and is available for download.