Yes your turning radius will be reduced. That isn't the end of the project though. By removing or changing the stops inside your steering gear box you have to determine if the added movement of the Pitman arm will cause any of the other parts in the steering linkage will bind or run out of travel.
I have a two wheel drive pick-up that takes a ten acre field to make a U-turn. This is because Chevy who wants to sell a lot of trucks but hates having more than one part on the shelf to build a truck, decided that the they would use four wheel drive parts on the two wheel drive truck. So my truck front wheels can not move any more than the maximum angle that the constant velocity joint in the IFS four wheel drive axle will support. If I were to change the stops in my steering gear box (the ones on the A-arms and frame are for collision and potholes to limit damage to you and the vehicle), then I would discover that my tie rod isn't long enough to reach any further without running into other steering gear parts and the oil pan.
I can not calculate anything with out a bunch of more numbers such as your pre-modified angle on both sides of the car, and the new angle, also from both sides of the car, it's wheel base, and track (since both tires do not turn the same amount).