Is this on a 383-400 block? I remember years ago "Challenger340" did an article on putting a 440 crank in a 400 block to make a 451 and the taller counterweights of the 440 crank would usually hit in the area you were grinding on in the photos. On his build he would put a large chamfer on the crank counterweight to gain clearance in that area before the crank was balanced.