2 types of GT40 iron heads, not talking abou the P

[Hethj7]

I am just finding out that the GT40 head found on the Cobra had 60cc combustion chambers while the GT40 head from the lightning or crate motors had a 65.5cc combustion chamber.

Most things I read never distinguish between these heads, they just simply refer to the GT40 iron heads. So, is this info correct and what other differences are there between the Cobra and truck versions of this head? And, were these (the cobra, lightning, and crate motors) the only sources of the GT40 irons?