Then all you need to do is make these changes in SQL EnterpriseVaultDirectory:
update the StorageServiceEntryID listing in table VaultStoreEntry to point to the new EV server for the VaultStore,
update the IndexRootPathEntryID listing in table IndexVolume for the correct index FolderName to point to the new server's EV indexing location,
and copy/move the correct index folder from the old server's indexing service path to the new server's indexing path.
Doing a synchronization of mailbox from the task, while dtrace is running and before making the other changes, is the easiest way to identify the folder name; if there is more than one index on the 'old' server and not all are going to be moved.
Deleting the task from the old EV server and recreating on the new EV server is much easier than trying to update the directory database entries for the task configuration.