I would be concerned with the unleaded only gas of today. I was always led to believe the old regular gas lubed up the valve seats. Most of the engine work these days includes putting in "hard valve seats" in the heads. Old timers with old equipment put a quart of diesel in a tank of gas these days. They sell lead additives for it too.

the top grade gas today should handle most muscle cars. the high compression engines of today are about the same or higher compression.