Making power out of the 318
Also… a flat top offers better flame propergation where the dome may-MAY inhibit the flame travel. This is dependent on some height, shape and sharp edges.
Sometimes a dome can not be used because of its height and shape is not going to work/fit with a closed chambered head, like an edelbrock. They can work and probably do best with an open chambered head like the early X, J etc heads.
For a good compression ratio on a street machine, 10-1 - 10.5-1 is what you’re looking for. This will run on 93 octane.