Is it really a question of octane with a low compression engine or is it more trying to find a non-ethanol fuel. Like John said "marine " gas, it's available at the pump around here. I used it to run my 327 on for the initial start up, costs a little more but non-ethanol.
Avgas has been around long before ethanol was added to highway fuel.
Marine gas has the same non-legal issue as non-highway avgas or farm diesel does, but it's harder to drive your car up to the fuel dock.
