The PV 12 doesn't need much of a rehab. If anything I'd replace the output caps and you'll have a whole new preamp. :)
It was a significant step up from the 10 thanks to multi-stage voltage regulation and increased heater capacitance if memory serves.
But it has a juicyness and midrange warmth you'll be hard pressed to find anywhere else.
It may also be time to replace the electrolytic caps, of which they are few.