Magnum in 70 Dart, can't keep it cool.

I had the same problem with my 73 dart. Running around town idling ect was fine. Get out on the highway and put some sustained load and it would get too hot. I had a stock 26" 2 core copper radiator. Replace it with a Griffin 2 core aluminum radiator and a Mrgasket high flow t stat and it barely gets warm now. Your radiator looks pretty good so I would look at getting max air and coolant flow through what you have. High flow t stat and seal all the holes in the radiator support so all the air has to go through the radiator. Fans and shrouds can actually block airflow on the highway. So you have to find a balance. AC condenser also blocks air and adds heat to the system.