Speedo cable housing threads are pretty much standard from one make to another. Why not just buy a cable/housing assembly for a long wheelbase truck of some sort that's a few inches longer than the one you have? That would probably be more reliable, and not much more costly than patching on what you have.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!