Hi,
Correct. ASASM should migrate automatically configuration about ACLs if there is NAT about it is pretty much because version and not model.
You can refer to NAT configuration format in following links:
https://supportforums.cisco.com/document/132066/asa-nat-83-nat-operation-and-configuration-format-cli
https://supportforums.cisco.com/docs/DOC-9129
And here are Web-Based NAT Migration Tool to obtain the similar results about NAT upgrade:
http://www.packetbin.com/scripts/ciscoPix84NATGenerator/
http://www.tunnelsup.com/tup/2013/05/18/nat-converter/
Johan.