Help with 340 compression + cam change

I see and not a bad idea considering how deep your getting into it.

Well, if I knew where the piston sat in the hole or above or at zero deck, of the hole, that would basically be the missing calculation number. (To a lesser degree, how wide the cylinder head gasket is.)
Do you know the height of the piston? Or exactly what piston it is. That would help some and from there , In theory, working with the manufacturers listed deck height, we can do the math from there.
It would not be exact, but it would be an educated guess.

A known piston height really only leaves 1 thing to guess at. The factory said there deck height is 9.6 - 9.58? Then minus the .040....