The installation sheet I linked-to above shows the "normal" holes for the GM by-pass oil filter.
The connection of a by-pass oil filter into the port on the head that goes to the rocker-arm rail is a common "work-around" but not described/sold by GM.
Here is the installation instruction for that "Rocker Arm Oiler Kit" line into the head. People also used that kit on high-pressure 235/261 engines - I think in attempt to get oil to the rocker arms when the internal oil lines were partially blocked.
