Check the casting numbers link on the left column of the web page. You will find that a lot of heads have the same valve and port sizes but the chamber volumes differ. Generally speaking for any kind of performance increase you might as well start out with the the smallest chambers as they offer the higher compression. That also allows you to unshroud around larger valves and not end up with as low compression ratio as you would have if you started out with the big chambers. Just about all the 230 and 250 heads had the same size ports and 1.72 / 1.50 valve arrangement. Minor differences would be the chamber sizes and accessory holes depending on the year and original application of the engine.
Mike
