1976 Dart Overheating and other issues

Ok I will definitely be changing the belts. The belts are three different brands embossed ( Goodyear, Dayco, and some other I can't make out). This is a 3 pulley car. I have factory AC and Powersteering. Trying to research online all 3 sizes to get.

Also, when flushing the radiator, I see three outlets at the bottom of the radiator. A plug at the drivers side, then moving to the passenger side a pipe that I assume runs to the heater core? and then next to it the rubber hose running to the water pump. Do I pull all 3 to flush the radiator?