5.3L Stock Head Flow

I searched all kinds of '5.3' 'stock' 'flow' 'head' terms, but I got tired of looking at all the threads without any relevant data. Most threads were in regard to how much compression would be lost by simply swapping to LS6 heads.
How much would I have to mill LS6 heads to maintain (or increase) my existing compression raito? Do I run into any problems with milling them too much? What about P-t-V with say .583 lift on a cam?


