I agree with Doug on this subject. Leaded gas was touted to add some lubrication to the valves which was supposed to make them last longer. I maintain numerous old cars & trucks for customers that have the original engines and they run fine. Several are driven to car shows from So Cal to Reno and las Vegas.
There was a article in Vintage Truck on this subject a while back. Essentially high performance engines could have problems with excessive valve wear. Most of the early 6 cylinders don't fall into this category. If your engine is going to be rebuilt and some of the seats have excessive wear, install the hard seats, otherwise leave it alone.
Fred
