We're doing a head machine job on the 427 to plane the surface and stop exhaust manifold leaks. During this job, we're thinking about installing hardened seats and stainless valves, as recommended by our mechanic (his quote on seats and valves about $400-450). I've heard various opinions on the need for this in an old engine. I would probably install them if we were racing it or dragging it or running the engine hard, but we don't drive it like that. What do you lot think? I searched the forum about hardened seats and found some good info, but no real discussion as to the need for it. Thanks in advance.