The oil line in the first pic goes through the water jacket and supplies oil to the rocker arms. The other end of that circuit can be found where the two rocker arm shafts connect, the part with the steel line connected to it. The sheet metal plate on the driver's side of the block is an "oil distributor" which supplies reduced-pressure oil to the tube that goes through the block. The port beside the oil distributor with the bolt screwed into it provides a pressure reference to the dash gauge through a small-diameter line, and also provides a point to attach a bypass-type oil filter. The return line for the filter attaches to a port just ahead of the oil distributor, near the oil pan rail.
Jerry
