Hello,
If you are going to begin a new SW development, K60DN512 is supported in the KSDK and is pin to pin compatible with K60DN512Z, so it's highly recommended that you use the new device, which improves some peripherals and fixes silicon issues.
You have all the changes between both devices here:
http://cache.freescale.com/files/32bit/doc/app_note/AN4445.pdf
Regards,
Santiago
