What and where to clean up Edelbrock RPM's?

crackedback said

Even with positive deck piston, I NEVER use those open chamber heads. In fact, every set I've ever possessed, the entire chamber gets milled off.

Lots of ways to skin a cat.

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I'm trying to understand and wrap my mind around this, so please excuse the extra questions.

How would a quench pad recessed into a head and a theoretical .040" piston to pad clearance be worse or less ideal, than a head with its block to head mating surface be the quench pad and a theoretical .040" piston to pad clearance?

I'm not opposed to changing what I purchased, i just like to understand why. I do value the information and appreciate everyone's time.