Mopar performance single plane fitment on a magnum

Hey guys
Another question about this manifold.
This is the only one I can find to fit a magnum.
http://www.summitracing.com/parts/dcc-5007380/overview/?ibanner=MobileSwitchNo
It says it needs an adapter plate to fit the 4150 carbs. I think most of the carbs now days are 4150 style square bores. Anyone know if there is a better single plain manifold to fit the magnum
Not sure why I need an adapter plate. I can grind the intake square or maybe because it's the bolt holes don't align.