Here is how the cable mounts, there are holes in this location under the dash for this purpose. This is a 7k mile fire truck.
https://www.flickr.com/photos/advance-design_parts_co/15295057304/in/album-72157631870734114/
Factory look.
https://www.flickr.com/photos/advance-design_parts_co/17037284497/in/album-72157651722976780/
I know a couple vendors carry them, they come a bit long so you can trim to fit. I don’t have one handy to measure.