1979 Super Six start issues

We have a 1979 Super Six put in a 1972 Duster. The motor has always started hard but it is to the point of ridiculous now. You can pump it 50 times and nothing but crank, crank, crank. It will start eventually. But if you pull the aircleaner and prime it it starts right up. I'm thinking there could be some part missing in the carb but not sure. Anything else I should be checking. thx matt