A few suggestions and questions:
Read the very long “Mercedes electric fan” thread in the questions and answers.
Search for and read the Stewart Components cooling tips.
I assume you are at an altitude of 5000 feet and air temperatures in the 95 to 105 degree F range?
Will the car reach 230 degrees coolant temperature idling in your driveway on the hot days?
Has the car actually boiled over and ejected coolant?
What antifreeze make and water mix percent is presently being used?
It there a modification that prevents you using a factory stock fan?
You might ask around among friends and family as to whether someone already owns a wind speed device like the Kestrel, and a good IR gun, preferably one that also has an external type K thermocouple probe too. If not consider purchasing these.
