Since finding what you need to install is not easy, here are some
directions. I have the same os x version and ruby version as the op.
For future searchers these are the steps:
1) Slide the "Mac OS X Install Disc1" into your drive. A window that
says "Mac OS X Install Disc 1" will pop up showing you the contents of
the disc. Drag the window open as big as you can; or up in the menu
bar, click on View>as List.
2) Click on the file:
Optional Installs.mpkg
It's not inside a directory, so you shouldn't have to go searching
through any folders.
2) A wizard will lead you through the install. When you get to the page
that says:
Custom Install on "Macintosh HD(or whatever destination you chose on the
previous page)"
...click on the arrow to the left of Applications to reveal a list of
choices.