will theses K-members work..

You have brake parts, suspension parts, and steering linkage parts. The steering linkage swap is complicated by idler arm connect at K member and pitman arm to steering gear. I think the early power steering gear is where the pitman arm issue lives. Manual steering might be non issue ( I forget ). Welding a different clip on the k member for later type idler arm is a solution there.
I don't think the later model K is direct bolt in to early A. Frame rail/bolt spacing different? If that is correct, a larger/wider K with the same single bolt ear for idler arm would have to be a 67 K member. That clip changed for 68 up.