Hi ccbrown
I agree with Shane that PWHT may not be required as per B31.3. But you may also consider that if this job requires the use of Piping Inspection Code (API570), then you may allow the customer's engineer (or Piping Engineer) to enjoy his privilage :)
Just to remind, API 570 states "Piping Engineer definition - One or more persons or organizations acceptable to the owner or user who are knowledgeable and experienced in the engineering disciplines associated with evaluating mechanical and material characteristics affecting the integrity and reliability of piping components and systems.
The piping engineer, by consulting with appropriate specialists, should be regarded as a composite of all entities necessary to properly address a technical requirement.
Joey