Yes I dunno but I always adjust my carb at idle once the vacuum rises it’s highest, then out a .5 turn. But on this carb I reach the highest vacuum reading with the screws all the way in!. Is that telling me something?
The Carter style carbs usually like 2.5 turns out or there abouts to start with. I would make sure the jetting is stock to start with before you move higher or lower on the jetting. When you go from park to drive it should only drop 50 rpm when the idle load setting is correct. If you need to turn the idle screws all the way in you have a problem some where.