Never had to use anything like that on OS7-OS9, but, while on OSX, I've used Araxis Find Duplicate Files and for folder content comparisions - Araxis Merge. For large image or archive file comparisions - Hex Fiend (2.1.2) All Intel, although early Araxis versons were PPC too. There's also an app called Dupe Guru, but it somehow didn't convinced me.
Araxis FDF calculates each file's hash on the fly, but, unfortunately, all files that contain resource forks only (many OS7-9 apps) are recognized as 0B in size and all will have the same hash.