On my 73 318 block I have cast iron heads 2843675. These were used on 67 318s and 68-69 273s with 2-bbl carbs. 1.78 intake/1.50 exhaust. Small chambers 62-64cc, small ports. I had Basko Engines in Gilbert AZ open valves to 1.94/1.60, polish bowls, used lightweight valves, 320 springs. They did...