bore to bore numbers

i know center to center is not the same accross all cylinders. i believe 1-2-3 and 4-5-6 are the same and slightly longer distance between 3 and 4. it might be that they are paired 1-2, 3-4, and 5-6 being the same with slightly more between 2-3 and 4-5. either way it is not the same all across.