...had to go with stellite valve seat inserts and stainless valves, or maybe the reverse? It was a long time ago.
It was the reverse. Actually all you need is the hardened valve seat inserts to prevent valve seat errosion.The valved face has the stellite on it to increase valve life because of the heavy duty requirements of a marine or truck engine. The valve face without a hard seat to come up against it, actually pulls tiny bits of metal from the valve seat that it seals against and the valve gradually sinks into the valve seat metal. The lead acts kind of like a lubricant and prevents this errosion. If I were rebuilding an old engine for marine use, I would use sodium filled valves with stellite face, and hard seats.