Because of the difference in distance between the carb and intake valves for middle and front or rear cylinders on these motors cylinders close to the carb could be running rich while those farthest away run lean.
One of the reasons for going dual carb is to achieve more consistent mixture across all six cylinders. Properly sized and tuned I would expect it to make more power and run up that hill a bit better. Might even get better mileage.
