See, where I disagree here is kind of my point. A steering gear doesn't turn left, right, etc. It just rotates. How that translates into steering is based on which direction the pitman arm attaches. So perhaps cutting another key into the 4WD arm would just about eliminate the splines. Still, if you were making an arm from scratch, you should be able to get one just as strong as the stock 4x4 arm, but clocked 90* to allow crossover.
It sounds like the 2wD spline is a stronger design, with is one reason to go to it. I doubt ORD is getting their arm manufactured. It's probably stock for one of the vehicles already mentioned in this thread (actually 2, since they sell 2 different drops).
From pictures floating around, it looks like the high clearance crossmember is only needed for short lifts, straight drag link, etc. It seems like with 4"+ and the bent link it can be made to work.