Idle fuel mixture setting for 68 250 Chevy?

the best way to set the idle mixture screw is with a gas analyzer. setting the mixture to 14:1. if you dont have one use a vacuum gage and set for the highest vacuum. If you dont have one of them then turn the screw in til the engine starts to stumble. then turn the screw out til the engine starts to stumble. turn the screw back in half the distance. that will be your best setting. Any leaner and the engine wont start, any richer and the engine will flood.