Canadian cylinder head difference?

[37 Coupe]

I took the head off of an engine today that I have had for awhile to check the bore etc. So it is a Canadian block serial # is CA 84810 and my question is were the heads made different in some ways to run warmer? Hopefully the picture below will show the coolant passage in the center is blank,not an open oval shaped hole as is the gasket and couple other heads I looked at.It may look like it in the picture but it is not brazd or filled in it is solid cast iron. I do know that the engine when I got it had another feature or two that was original for cold weather operation like a tall oil breather cap I researched at the time.