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The iWork applications - Keynote, Pages & Numbers - can only open AppleWorks 6 presentation, word processing & spreadsheet documents, respectively. They will not open any other type of AppleWorks 6 files or any AppleWorks 5 or any version of ClarisWorks files. All versions of ClarisWorks & AppleWorks 5 cannot run in OS X. An Intel Mac can't use Classic, so you would have to use AppleWorks 6. AppleWorks 6.2.9 (the current version) can't open all ClarisWorks 4 or earlier files. It gives an I/O error. There doesn't appear to be a way to predict which files will cause problems. I've had it happen & not happen with all AppleWorks file types. These files can be opened by any other version of AppleWorks 6, so a good choice would be AppleWorks 6.2.4. AppleWorks 6.2.4 is the earliest version stable in OS X. Avoid 6.2.7 - very, very, very buggy!
Hardcore Mac is selling AppleWorks 6.2.4 the last time I looked. You also can sometimes find AppleWorks 6 on eBay, but it might be difficult to be sure it's no newer than 6.2.4 and has an OS X-aware installer.