These items are rolled in with the next major "retail" OS release. This system, once understood, explains why many Mac OS installer discs will not work on other Macs. They lock that down a bit but the retail ones are more universal. The appear to be continuing this somewhat in the era of App-store delivered OS updates, with some modification.

Whatever the case, Apple has never made it easy or simple to go backwards to a version of the Mac OS that pre-dates the hardware launch date. Sometimes you can find a few enterprising users with time on their hands that have figured out how to do it by moving certain files to the old OS, etc. but that's the level of time-sinking geekery you are going to have to resort to in order to do it.

FWIW, HTH,

carey