To simplify cam bearing manufacture,  replacement cam bearings 2-4 are the same with three holes each.  The center cam hole in the block is the only cam hole that has three oil feed holes which must be aligned with the three corresponding holes in the cam bearing.  The rear cam bearing hole has two holes and simply requires that two of the holes in the cam bearing align with those. Cam holes #2 and #4 in the block only require the single main oil feed hole from the mains needing to be aligned.  The front cam bearing is wider than the rest and only has one hole in the bearing to align with the oil feed hole in the block.