Visual Studio Tools for Office (VSTO) version confusion

Can someone please tell me about version binding between VSTO and target office version?

I am using VS2008 with VSTO 3.0 to build and deploy an addin for Outlook 2003. I am completely confused about what is required on the target machine:

Runtime of VSTO 2005 SE or VSTO 3.0?

.NET Framework 2.0 or 3.5

Primary Interop Assemblies from Office 2003 (I think)

In the end, I need to tell the customer's IT department how to deploy the addon using their own script based support system. They don't want to have an MSI package.