Dont waste your time with the bottom of the port, There is almost no gain in flow lowering the floor.
Concentrate your effort on removing the thermactor bump, blending the bowls, and shaping the guide boss. When you shape the guide boss, dont trim it at an angle or remove it, it makes it a pain in the ass to get a good cut with the cutter.
Here is a shot of my GT40 heads I ported for reference:
Keep in mind as well, your going to be putting a lot of money into those heads, and the outcome will not be worth it.
When it was all said and done, I had about $8-900 into my heads, ad I didnt even have as much done as your planning to do.