If i go this route, I will make and add a spacer here on each side. You can buy replacement cables fairly cheap. Down here in west Texas stuff doesnt rust that bad. I bought new cables for my 67 restoration even though my originals were useable. I am using those on my sons 69 and modfing them to accept the disc brake setup.
Thats my photo above. No spacer necessary. All I had to do was drill the hole a bit larger slipped right in like a champ. I just did my first ride yesterday. So far I love the swap.