Milling of a 810 casing W-2 head

Its cold and i'm thinking of the 360 i may build in the spring. Its flat top piston .005 in the hole and .030 over. I have a set of ported W-2 heads and would like to know how much i can safely mill them. Anyone with experience? I don't believe they have ever been milled on the chamber side.
810 castings are early heads. I would not mill those. IMHO
Excerpt from the stroker small block book.

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