Hippie is right. A well designed dish piston will have a flat top on the portion of the piston that corresponds to the flat part of the chamber and the dish will be where the open portion of the chamber is. This gives you quench in the non chamber area.
In the piston pic area 1 would be the area that you would want to get the ~.045" piston to head distance with. This part of the piston top should correspond to the flat portion of the head.
2 is the dish and should be the approximate shape of the chamber portion of the head.
They should match the same numbered areas in the pic of the head as best as possible. NOTE - the piston and head I used for examples don't match each other they're just the stuff I had pics of.