Some of us with 440s have experienced the off idle dead spot with Edelbrock 750s and 800s and it's related to particular engine builds, not a random defect in the carb as I haven't heard of this problem affecting stock 440s. I came across this video and I'm going to try this mod after the weather washes away the salt on the roads.
https://www.youtube.com/watch?v=aX2v-du5ias&list=WL&index=55
Has anyone tried this before?