Cylinder Heads - Cat C15, C16, C18 and 3406E
 

I have some doubts about the C15, C16 and C18 engines:

Do they use the same cylinder heads? The differences between this models are just in cylinder bore and stroke?
And what about the 3406E with C-15 and C-15 Acert?
(I’m not from USA and it is very difficult to get information about those engines here)