68 kframe vs. 73 & up

So with the 67 pitman arm thing, is it just the mount that is different or is the whole arm different? I have 67 Dart now with what I assume to be the stock K member (modified with welded on spool type mounts), but I have a 73 K member ready to swap in at some point. Will I need to be getting new arms or will the existing arms just mount differently in the new frame?