I spent a while trying to research your question and gave up as I only have ASME IX editions back to 2004.
As P5A, B & C are now classed as separate P numbers your old P5 PQRs and WPSs cannot be used as they are.
You, or a Welding Engineer (if you are not one yourself) needs to do extensive research because it is a pretty comprehensive topic.
I don't know how to attach so try Googling - Inquiry 09-490 and also this link
http://www.sperkoengineering.com/html/2009_addenda.pdfCheers,
Shane