I am looking for the best way to manage and report on Windows server licencing in SD+

We have a mixture of server versions 2003 Standard 2008 Standard 2008 R2 and 2012 R2.

We currently have more instances of Server 2003 installed than we have 2003 licences for, however we are covered from a Microsoft Licensing point of view as we have more than enough Server 2008 licences to cover them. Likewise 2008 R2 and 2012 R2.

When I run the Purchased v Installed software report it shows under licensed on Server 2003.

Is it possible to assign a server with Windows Server 2003 installed to a Windows Server 2008 Licence?