the carb looks like it sits off to the one side a little more then the other,,,like maybe the mounting holes on the intake are drilled of center ?????
i can see you have the proper spread bore intake,,they do make a spacer/adapter about 1/2 inch thick,,to use on intakes that are not spread bore design, with a spread bore carb like yours,, but i dont know if the spacer/adapter is wide enough to cover the part of your carb that is not sitting on a solid surface,,