Look for the new type of antifreeze that changes color when it begins to loose its heat transfer properties.
Water is what mechanics first discovered at the same time they discovered oak wood made solid frames.
Any national brand of antifreeze will perform if you follow instructions. However, if the engine has never been flushed in 40 years and the car is winterized each year, some of the ducking can be obstrued by gum by as much as 70%, thus reducing the heat dissipation capacity of your rad because of a lessened quantity of coolant forced against the honeycomb.
Get a professional flushing, ceplace the rad cap with the right psi pressure and your Temp gauge will hardly ever reach mid point.
Best regards and keep cool.