Hi Steen,
we've already discussed about this case for client computer data migration from old 7.6 database to a new 7.6 database, when client PC GUID will be preserved https://www-secure.symantec.com/connect/forums/partial-migrate-data-old-ns-new
To save an old client PC guid, you have to use "Resource" - stand-alone replication rule, then client PC data with its keys will be successfully replicated to a new server and in case if you will redirect this client PC from old NS to a new NS, then client will has same GUID, since client keys are available in a new database.
Note! Data connector will doesn't import/export client PC data with its keys, therefore if you will redirect client PC from old NS to a new NS, then this client PC will get a new GUID.
Thanks,
IP.