1953 Flathead 6 fuel?
 

I have a 1953 plymouth cranbrook with the flathead 6. Ive been told that regular gas is fine, ive been told that i need premium, and ive been told i need lead additive. I have no idea if it has hardened valve seats or not, ive been running premium in it so far, anyon ehave any advice? thank you

Regular unleaded with lead additive is where I would start. If there's no pinging or knocking there's no reason for better fuel. You would not no if it has hard seats unless you pulled the head or talked to the person that rebuilt it last. Lead additive is just a safe assumption.