Right now I have 452 heads. At first was thinking to get 906 better compresion and flow, I THINK ? Now I have heard about the new cast iron heads made by mopar perforamce same as 906 heads better flow and bolt right on. part number P5249114 sold at summit racing. Does anyone know anything about these heads? So of the three which one will improve the perforamce of my 1972 440 in a 1965 ply bel 2 ? also be the best heads to have with the new 6 pack thats in the car future? The 452 heads, 906 heads or the new MP P5249114 heads which one to get? love to hear people thoughts.