Again: Unleaded or leaded fuel for mid 70's /6?

There are endless articles about this all over the internet. The number ONE cause for valve seat recession has nothing to do with leaded gas being removed from the market. It's people not changing their air filters when they are due. Dust and dirt get into the intake tract and through the engine and combined with the intense heat of the exhaust valves the dirt particles basically grind the valve faces and seats into oblivion. Hot rodders seldom see valve seat recession because they are normally on top of filter changes and do things like keeping timing advanced and mixtures a little richer which leads to a cooler running engine. Heat and dirt are the two enemies here.