Correct, the 340 and 383 cars got the smaller primaries on the AVS carbs from the factory. This has always been the case. Just open up a Factory Service Manual from this era and you'll see. Only the 440 got the bigger primaries. I have a '69 383 AVS carb on hand and it has the center air adjusting screw. I uncovered the lower screws and put the regular screws in there for mixture adjustment. This could have been a California model or something I don't know?
