70 Dart A/C not blowing hard.

I'm checking the wiring on my 70 Dart project and noticed that when the a/c fan is blowing, it's not moving much air. The fan motor sounds normal and it has low and hi speeds. It seems fine for the heater but not enough air is moving for a/c. Is there a chance that the vacuum lines have a problem? Does anyone have a HVAC vacuum diagram for 70 Dart with factory air? Any other suggestions?
Arnold says that global warming is coming to California, I want to have a car to cool off in!!!
Thanks, Doug.