8.3 and higher versions is based on object-networks so your entire nat will be based on that ( as an example if you have names enabled before the upgrade, all of the names will be translated to objects automatically)
Also if you have nat-control enabled extra nat statements will be added to your configuration as Nat control is disabled on this higher versions so it's a must to disable it before the upgrade.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...