Hello !
The AN2726 is written for the S12XDT512. You don't need to change the code.
You need to follow the guide to create the mailboxes you need.
Everything is explained is a lot in details in the AN2726.
The software is available with AN2726SW.
Alban.
AN2726SW Source files for AN2726 in ZIP format FREESCALE zip 155KB Rev1 Released Date 3/23/2005