There was a time when GenShip didnt pass in a PackLine and I needed ShipDtl to print a specific line, not the whole batch.
Here is what I did.
You can apply something similar probably to your scenario.
Basically:
When you hit the JobOper Data Directive - you can update a column you make on JobHead called JobHead.CurrentOperationRowID_c and you assign the JobOper.SysRowID to JobHead.CurrentOperationRowID_c and then in your RDD you simply JOIN JobOper and JobHead by those fields.