I put Carrillos on my 6.4 this past winter. When test fitting, there are some cast nubs (4 total if I remember right on the outer walls (skirt) of the block. Only 1 nub actually made contact with a rod, but the others were close so I shaved them all down. The cap end of the rod made contact where the bolt head was just as a reference. Take in account the rough casting can be slightly different from block to block.