Porting 596 Heads
I'm coming to this thread WAY.....too late but here is my opinion. First the head needs to be ported for the us it is going to be used for. Your description of you build would translate to (in my book) good 3 or 4 angle valve job, blend last cut into the as cast port. Stop! In the first picture were Mp show you to cut on the common wall.....I would do that but not get crazy! more of a clean up in that area. Exhaust STOP DON'T START!!!(yeah i know too late.) In my opinion grinding on the floor of the exh port is a BIG negative, even if it has casting flaws. Just don't do it! As in the intake blend the bottom cut of the seat into the as cast and wake away.
Remember, he is not trying to make bit HP With some big camshaft.
Doing what i have said will give you a noticeable improvement without the negative bottom end lose.