What spark plugs for 340

aviation fuel is designed to atomize at low temps/altitudes and evaps even faster under a hot hood!. I am sticking with alcohol free 91/93 even that's bad compared to the gas they sold 50yrs ago for these engines!!!
Thanks for the info,,,,,the AV fuel I think is around 100 octane. Plus it has some lead in it, that should be good for the older engine,,, I think ,,,, The guys at the airport say it works good in old tractors, and lawn mowers. Also use it in your portable generator for power outages,, it will last forever, not go sour like today's pump fuels.