Factory 391' are fairly flat 60/40. Do you already have the barrel? A 32" barrel on an auto loader with a really long receiver kinda makes the gun look super long. Just my opinion. Thirty inch barrels will get the job done.
I would bet after you put it on paper it will shoot High left at 15 yards by about three inches and may be four. That is center of pattern to center of spot you shoot at. Thye just seem to always shoot left.