Different Heater Boxes

Hello there. Hoping someone with more knowledge on the heater boxes in the A bodies can lead me the right way. I have a 71 Duster that im putting a 440 in. This car had the factory ac option slant 6. With this setup you have to remove the WHOLE ac setup with the Heater box. I'm assuming the heater box is different for the ac/ non ac cars. I know a guy who has a heater box in a 73 Dart that will sell me pretty cheap. Would a 73 dodge box work a 71 Plymouth?

Thanks !