I checked the 1942 Canadian carrier we have. First of all, I should say I got it wrong. I assumed the long fitting was solid. I just found it's not, it's hollow, which completely invalidates what I said above in the deleted post.
Anyway, our carrier has the fitting installed in the outer vertical port, as all the drawings show. There is no grub screw installed in the horizontal passage between the two vertical ports as shown by the "straw" photo below.
I have attached a sketch of the fitting. The tubing extension on it is 3/8" OD, which is a fairly snug fit in the vertical passage coming up from the pump. I would guess diametral clearance as about 1/32" based on how much it moves side-to-side in the passage.
So it directs most of the oil from the pump up into the cooler but also allows some flow through the gap between the tube and the passage wall to the crank brgs, etc. Just as well, as if there was no bypass, I think starting the engine with the engine and cooler drained would cause bearing damage by the time the oil got all the way around the circuit.
Malcolm