73 dart v8 removing heater and a/c

The first thing you circled a nothing to do with the heater core. the hoses you have to remove. Now if you look inside right side where the air vent door is there is a rod that is shaped like a hook on one side (top) and has a bolt on the bottom (under the vent). The hook hangs on to the cowl. Once you unbolt that it should come out.