The first thing to look for is vacuum leaks. Use gas from a Propane torch (unlit) and move the tip around all the gasket surfaces like the intake manifold to cylinder head junction, carburetor base, and vacuum lines that might be attached such as the windshield wiper motor under the dash, etc. If the engine smooths out or speeds up when the gas gets sucked into a leak, you've found the problem. Also check the ignition timing- - - -late timing makes it hard for an engine to idle properly.
Jerry
