Tom, as good as you are with fabricating aluminum, I'd bet you could trim those ears off the base plates and get them to look pretty clean. Just a thought.
Currently I am thinking of making a set of spacers that have the smaller pattern counterbored and use socket head allen bolts to attach them.
Then I can add the wider pattern to the spacer and just bolt AVS carbs to the spacer without having to modify anything on a carb. I think this would be the best of both world's.
I have one really nice 4640 AVS and if I can find another one I'll probably go this direction.