Door wont lock

[Andyboy]

My 62 gmc doesn't have a lock handle on the driver side, just the passenger side. I can't lock my driver door, with window down I lock it from the inside, then push the button and it opens. Is there something missing? I've also tried to switch the buttons, but the rod attached to the passengers side button is longer. If I buy a lock button with the rod longer than what it has now, can i cut it to size and be fine and will it lock? Hope this makes sense.