I bought a 65 GTO that had a 67 400cu in motor but was upgraded with the 65 tri-power . This motor has 061 heads on it. These are the open chamber, big valve heads. The block code is VX, and research told me that it is a 290hp motor from a Catalina. My question: What was the purpose of having these big valve heads on a low horsepower motor? Does anyone know what other 67 motors these heads are found on?