are all 781 castings open chamber heads?

Here are 2 pics of heads.....they look different to me(chamber size)
is one just shaved more?

 

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If one 781 casting is open chamber, they all are. That's the beauty of casting numbers... they describe which casting they are... things like chamber design are a feature of the casting.

Those look like really low-perf small valve truck heads. I would not use them for a performance build if I could help it.