How do you know that? Have you inspected them? If his heads need much more than being freshened up with a good valve job, it's gonna get expensive, quick. Without good guides, reground seats won't last long. Can his seat stand a regrind without sinking the valves too far? Are they sunk too far already? He's easily facing 1K plus in parts and labor if his 50 plus year old J heads need a complete rebuild. So anything here is a guess at best