How do I edit the BaseSystem.pkg file from the Leopard Install Disc?

[macintoshlover]

I wanted to add the patched extensions to the Install Disc so that they get installed during the installation and save me from the hassle of doing a post patch. I know that I would need to add the modified extensions to the BaseSystem.pkg file in the Install Disc. However when I extracted the BaseSystem.pkg file using Pacifist and then right clicked it, I do not have an option the "Show Package Contents". Please help me how I can add the extensions to the BaseSystem.pkg file.