Cylinder Heads

[1965 Mustang]

I have to replace the cracked head on my 29 A. Going by the serial number my Car has a 1929 engine block in it. I got a used replacement head and noticed that the water passage openings in the new head and the cracked head I am replacing are slightly different. Most notably the replacement head is missing a round opening about 1 inch in diameter right in the middle of the space between cylinders 2 and 3. I have attempted to attach a photo of the 2 heads side by side. Does this difference matter? Why do 2 seemingly identical heads have slightly different openings for water passage. Thanks