Product : Replication Manager
Replication Manager product guide says that you can cross-mount from 64bit to 32bit windows 2008.
--- Replication Manager 5.2SP2 product guide p153 ---
◆ Replicas of Windows 2003 and Windows Server 2008 data can be cross-mounted between 32-bit and 64-bit systems as long as those systems are otherwise supported.
◆ File system replicas of Windows Server 2008 data can only be mounted on Windows Server 2008 mount hosts.
Having different service pack levels is not recommended. We would run into issues with VSS when the versions do not match.