Henry,
The 534 plate if maked "filter in" goes to the filter in side. "Filter out" is the returned clean oil from the filter that goes direct to the engine, thru the 534 plate.

The plug I think Matt has to make a cross drilled hole in the plate. I don't know off hand if it's the pressure side. Looking at the pic it does look like the pressure side but it would be unfiltered oil.
Jeff