Airflow thru the radiator at 65 mph is driven by road speed not the fan, unless the fan is blocking airflow itself.

Generally speaking temperature issues at highway speeds are water flow issues not airflow, but that assumes a factory designed cooling system as well.

I see you have aftermarket pulleys, that may be affecting the water flow. Looking at the pulleys they look like might be underdriving the water pump. If you happen to have a stock set of pulleys you might swap them in and see if that clears it up.

How many vanes on the water pump impeller? impeller count and pulley ratios are interdependant, if you run non-AC pulleys with an AC water pump you run into issues like you have. The non-AC pump was more impeller vanes so it runs ate a lower speed. AC pumps have less vanes and run at a higher speed to move the water.

They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.