Ebay Evaporator for 74 Duster?

Fill it with AC flush and let it sit a few days then blow it out. Fill something with water that will submerge it with the pipe outlets in the air. Plug one side and set your compressor pressure regulator to 100 lbs (when off and the pressures equalized it will have 100+ pounds in it). Look for bubbles in the water, just like looking for a slow leak in a car tire. I would only use an aftermarket evaporator or heater core as the last, last resort.