360 year differences
Like the compression and HP ratings, the head flow of the later 360's my be similar to the "J" but is not the same. But regardless on the flow, the "J" heads are more sought after so they are worth more to people. Just look at what they sell for.
But of course swingtown has the right idea on buying both, I was just trying to tell you the differences between to the two since that is what you asked.
Chuck