As you probably know, In AML 5.1 the attachments are controlled by Shared Services content server and one approach is to make the webdav content server act as a filesystem to which you can copy the files from a real filesystem location. Collogues have used BitKinex for migrating in the opposite direction (taking the attachments from the webdav content server) and I am not sure if it will help you the other way around. Also you will have to update to sas_attachment table on the sharedservices database.
Whilst I do not have code supporting your precise use case (Norkom to SAS AML 5.1), I do have code, shared by one of our colleagues, to support migration from 5.1 to 7.1. This may give you a good starting point for understanding the AML 5.1 side of things.
I appreciate this is not a full answer to your question. Let me know if we need to share the above referred code with you.