360 Head Casting Numbers?

Here is a list;
http://www.moparts.com/Tech/Archive/smallblock/6.html

The 2513894 is an "X"
The 3418915 & 3671587 can be "J"

The reason I say "can be" is I have seen some 3418915 as "O" and "U"

Also the 3418915 is the head Mopar used for the T/A head, the intake pushrod hole on this head are offset away from the intake port.