I saw these two carbs, both Carter AVS 4618S, which are for '69 440HP A/T non-air. I thought the '68 carbs had one idle mixture screw, and '69 and later had 2. Here's an example of a C9 4618S (March 1969 date code), with the two screws:
This one is coded November, 1968, and has one screw:
Here are the numbers on it:
Can anyone explain what's up with these carbs? I need a 4618 for my car, and it was built on September 4, 1968. Did they change something mid year? Why wouldn't one have one screw, one have two screws, and they both have the same number?