heres the 4426 carb i picked up off e-bay a few years ago, plugs still in it, never removed. I had the pri shafts bushed, then rebuilt it, stuck it on the 383 RR which is near stock and tried to adjust the vac/idle, would not respond to the top screw didn't idle bad, but went with the 69 avs that was on the car. I'd bet the dealers removed the plugs on a lot of these carbs to tune them in better back in the day.