If you try to launch NUM 4.04 under OS 9, it will tell you that it does not work with the OS. It will say to check with Symantec.
Norton Utilities Mac 5.0 works just fine with OS 9, and so does DiskWarrior 1.04.
The best of breed will be the TechTool Pro 2.5.2 version to be released any day now. It works very nicely and fixes more stuff.