Do not waist your time with hardened valve seats. That engine has run for years on unleaded fuel and hasn't need them yet. The only time to use a new valve seat is when the head is worn out and you are building a numbers correct engine that needs the original heads. If you plan to run this engine are top rpm with the bed fully loaded with sand, then add the seats, other wise save your money. Just remember, unleaded fuel became the main fuel in '73, but it was around way before that. Just for kicks, ask your local machine shop to show you a worn valve seat from the use of unleaded fuel.
