We did that routinely on round track race cars with wildly modified steering systems. Use a 3-cornered file and simply make two splines out of the wide ones- - - -there are usually four equally-spaced wide splines. Once the splines are modified, you can clock the Pitman arm one notch at a time to find the most effective position.
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!