Mopar magnum heads ?

[crazycuda]

I wanted to find out if there are any benifits to the later model magnum 360 heads over the old 360 j head. Its obvious that the ports are smaller but how much improvement did they do. I don't have a set here so I cant do any flow checks so i need some input. I know there is a handful of little things needed to be done to convert these heads to an earlier block but they all appear to be minor.