No you wont need to change the K member. If you do install the 73 up center link with that pitman arm and idler arm, you can weld another clip onto the 67 K member for the through bolt type idler.
A lot of us have got in a situation where we needed a pitman arm that Chrysler never made. It was said in a recent thread that a aftermarket vendor now offers that custom/adapter like arm configuration. Good luck
