Vapor lock is a major problem for the old classic cars. Ethanol has a lower evaporation temperature.
Unfortunately, running high octane gasoline in an old car is not recommended either. I am stuck.
Adding diesel to the tank seems to help. Unfortunately, the car smokes a bit. LOL.
I’m assuming you need a lead substitute also due to non-hardened valve seats pre-1975?
I run that CD-2 additive. If the car sits any length of time, use “Ethanol Shield” stabilizer. The best I’ve found personally to date.
My 65 Willys jeep handles ethanol free very well.
The Weber 2 barrel probably helps.