1972 Dodge Dart Vacuum

Hello, My name is Holland. My husband and I own a 1972 Dodge Dart Swinger. We had the engine rebuilt about half a year ago. The car could drive the mountain fine, and well. All of a sudden, it could barely make it up a hill. We had the carberator rebuilt and a new starter installed about three days ago. My husband put in new spark plugs and checked the distributor. He said that when he takes the vacuum off, where it is connected to the engine or something, the car works fine. It goes up hills. He said he can't leave it that way because dirt and grime would get clogged and screw everything we worked so hard for, up. So my basic question is are there any manuals to help my husband check the vacuum lines or any advice? We are broke for the next month and are trying to get this fixed ourselves. To get the kids to school. Thanks very much.