We owned the engine rebuild shop during the late 80's through 2000ish. We saw the switch to unleaded. We cut heads for hard seats but damn near every burned valve was from an exhaust leak....not fuel choice.
High octane fuel is actually harder to ignite and can be a pita if you don't have the compression to run it and the carb dialed for it.
I'd run non ethanol and never look back.
During that time frame I worked at a GM engine plant. I don't remember the year, when we came out with the high rail heads we had three different types of exhaust valve seats. One was the stock seat, trucks got the induction- hardened cast iron seats, performance heads got the stelite inserts. We also put the rotater caps on the exhaust valves. Not sure how much good they did...
