Power Brake Booster Question

There is a place in Sacramento called http://www.powerbrakes.com/

Tell them what you're trying to do and they will set you straight. I believe the power boosters are not the same but they can tell you. I have used these people and they sold me what I needed to rebuild the booster which had a hole in it. They're very friendly and knowledgeable.
I can tell you this, my 69 Dart and my 72 Duster have the same booster on both.
I'm pretty sure they didn't change till 73.