Rough Or Unstable Idle

Ensure there are no vacuum leaks.
Verify vacuum hose routing is correct.
Ensure idle adjustment is correct.
Ensure fast idle adjustment is correct.
Check vacuum choke break diaphragm.
Check choke valve operation.
Ensure fuel level is at specified mark on carburetor sight glass.
Check for fuel percolation.
Check PCV system operation.
Check EGR operation.
Verify ignition timing is correct.
Briefly remove spark plug wires individually to determine if problem can be isolated.
Check thermostatic air cleaner operation.