I think SNAT and SNAT automap existed even before 4.2:
http://support.f5.com/kb/en-us/archived_products/big-ip/releasenotes/product/relnotes4_2.htmlnew10
Enhanced support for Secure Network Address Translations (SNATs)
In previous releases, BIG-IP allowed you to automatically map VLANs to translation IP addresses during SNAT creation. In this release, you can now use this automapping feature not only for VLANs, but for one or more individual IP addresses. For more information, see the BIG-IP Reference Guide, Address Translation: NATs, SNATs, and IP Forwarding.
If you get stuck configuring this, you should open a case with F5 Support and ask for Paul Pfarr :)
Aaron