Last time I was at the airport fooling with planes, you could still get very high octane aircraft fuel, with a reasonable amount of lead.
The biggest difference, not the only difference, but the biggest difference, between very high octane gas for race cars and very high octane gas for aircraft is the point at which "vapor lock"
will occur.
Aircraft operate at high altitudes and low temperatures. At least the fuel has to be formulated for operation there.