Legally? No..
But it has been done.
Not sure why you want to shorten the pitman arm? If you don't redesign the rest of the steering geometry you will loose turning radius with just a shorter pitman arm.
Another option or alternative to cutting and welding is to cut it off and drill and ream a new hole in the now shorter arm.
The way I read the laws you can't modify any steering, not even to swap parts from another model vehicle, much less cut, weld, bend, or machine steering components. But if you want something different you have no choice but to make changes or use different parts.
When I do something like that I try my best to do it in a professional way, so you can't look at it and tell what was done, and most importantly; keep it safe.
Grigg
