318 engine identification

MOPAROFFICIAL said
Not all.
340?
My '70 340 has 3, a lot of 318's had 3, 360 were 3 etc.

That’s so strange. There has to be some sort of rhyme or reason to which got 4 and which got 3. Makes no sense. Different casting boxes at different foundries? My ‘70 340 has 4 but yours only has 3? WTF? I have to get to the bottom of this.