Nozzle drip at idle indicates not enough idle fuel, or idle bypass air, or both. A high idle speed will also induce nozzle drip as the engine starts pulling fuel from the carburetors main system.
You would have to test the carb on the 305 to know if it's really going to work correctly or not? If it has similiar vacuum at idle characteristics as teh 385, then it woln't be far off?....Cliff