If its holley, back the idle screws 1.5 turns (common starting point and probably on the rich side). Then, screw inward each screw .25 turns. Keep screwing inward till idle becomes reduced or rough or increased (sooner or later one of the above will ocurr). Back the screws off .25 and you should be done.
Verify the idle speed adjustment is correct. If you don't get any responce from mixture screw adjustment, the idle speed adjustment is probably set too high. Get the Idle speed screw adjusted correctly before mixture adjustment!
69 X-44 base coupe, ZZ4, 16lb nodular flywheel, Center force DF clutch + PP, Holley 600DP, Hooker super comp 1 3/4 ceramics, 2.5" dual exhaust w/ X-pipe, flowmaster 40 series mufflers.