The port spacing is the same but the mounting on the head is different. The earlier K use a piece that bolted to the head in each port, then the exhaust slipped over the top and used clamps to secure it. The later pipes went right into the head and used the more modern split ring type setup. The pipes will physically interchange if the appropriate pieces are used. How it mounts to the frame and mufflers etc is totally different as are the styles of exhaust and everything would have to be custom made.