Importing node_revisions records from version 5 to version 6
Instead of trying some convoluted way of exporting and then re-importing the data and maintaining all meta-data - have you tried simply upgrading the site to Drupal 6?

This has been heavily documented on drupal.org

When you do a major drupal upgrade, so long as there is a drupal 6 module for your functionality, there will be update hooks that alter the database to convert it to the new schema.

This includes CCK, revisions etc