for item fulfillment, orderLine is same as the line number of the item on the order?

yes

Are you sure? Getting some errors about not finding the match for the orderLine.

Code?

Trying to extract the SOAP request from the logs.

what are you basically needing to do?

To create IF from the SO using SOAP WS.

The problem with initialize is that I am already getting a SOAP payload to use. I add the authorization head and orderLine attribute.