[65chevysub]

I was looking for the same answer awhile back but didn't get one Anyways, there is a clip on the floorboard underneath that holds the cable out of the way. I will try to get a pic for you shortly.
They are kind of hard to see with all the grease on them, but there are 2 clips on the bottom of the floorboard. I have rear wiring in some split loom in mine and my speedo cable is outside of the clips.You might be able to use the clips for your cable. My cable goes through the floor below the "bend" in the floor. You can just barely see it nest to my shift rod.
Hope this helps