Alternate Content Copy
This project is not covered by Drupal’s security advisory policy.
UPDATE 31 January 2011: module abandoned, please use Features instead, it's safer and more reliable.
Alternate Content Copy alters the behaviour of the Content Copy module that ships with CCK. Once installed, the import procedure of Content Copy will allow you to import a complete new definition of a content type into a pre-existing copy of it, going beyond the mere import of new fields only.