milling 440source heads

I'm not an engine guy so correct me if I'm wrong, but my understanding of quench distance is the distance from the piston to the head. In other words, and amount that the piston is in the hole plus the thickness of the gasket. In your case that would be .120" for a shim gasket or .140" for a composite gasket. I believe the perfect quench distance is .040" to .043". That's why Mr Hemi suggested 0 decking the block (0 deck and composite gasket would be about perfect quench). Milling the heads will reduce the chamber cc's and increase the CR but it won't do anything to reduce the quench distance.

Now, for my understanding, is getting the quench distance correct any more or less important w/ closed vs open chamber heads?