C15A Cab 12 Speedo Question

[TCLARK]

Hi All
I am slowly progressing with the truck, and have found an old
speedo cable. Both ends screw onto the Cmp speedo and the
bottom housing. This cable will work but is a bit tight,
Does anyone know the proper length for this application.
The cable I have is 57 inches long. It will at least
be a big help if I have to have a new one made.
Do these cables go out to the front on the enginge before
bending around?
Thanks
Terry