I remember traveling in 1974 with a British engine engineering
consultant who was absolutely positive the US auto manufacturers were
going to be in for a rude surprise when unleaded fuels were foist upon
them by the EPA and the 1975 catalytic converter needs. He predicted
valves and seats would quickly fail creating a massive maintenance
problem.

It never happened. Hardened valve seats were used from the beginning,
and the reduction in engine contamination has given us longer service
intervals and incredibly long lived automotive engines today.

Where are the hardened seats for aircraft engines? Even something that
recognizes some fuels don't have TEL in them? I've lived with over 20
years of autofuel in my O-320-E2D (one of the first STCs from Petersen)
using low cruise powers, hoping to minimize valve seat recession. So
far I've been very successful.

The lack of a consistent airport distribution system to assure quality
for MoGas after 20 years is crazy. There must be other forces at work
that are not obvious to me.