As mentioned previously 72 and 73/74 B-body K-frames are totally different.
73 and 74 big block and small block k-frames are also unique having different motor mount off sets on the k-frame (see pics). Seems to me someone had also mentioned and provided pics of an early 73 k-frame with 72 style motor mounts.
[img]http://www.forbbodiesonly.com/moparforum/attachment.php?attachmentid=210883&d=1410749393[/img]