Lynn,
Here is a photo of the engine as I found it:
There is a standard 't' piece to mount the pressure switch and what looks like a normal fitting in the vertical passage, however this goes into the block around 1.5". For all I know this could be a post war mod, or a British Generator mod as this engine was used as an Altenator driver at some point. I will get a photo of the waisted fitting when I can and post it up. In my view the angled oil return hole used on carriers and a post war mod would just need to be a standard fitting.
The 59A block (1945-48) I have in reserve is a different casting with an angled boss ready to drill and tap into the main oil gallery.