Here is what Holley says: "Adjust the spring-loaded bolt and nut until the clearance is eliminated. This should require only a slight adjustment to minimize the clearance. Do not preload the lever. Excess clearance at idle is a very common occurrence that takes a minute to repair and when adjusted drastically improves drivability."
I would close the gap so that when the throttle is just opened, the pump arm begins to move but not preload. You are very close.
Once checked, I would put a vacuum gauge on the car, warm it up, and reset the idle screws to maximize the vacuum reading. On mine, I got 17 inches of vacuum.
What color cam is in the carb? I would get a set of pump cams and if you still have a stumble, just slip in the next larger one and see how that changes it. They are a 2 second change.