Fast Ratio steering Pitman and Idler arms

The fast ratio pitman is longer than the standard arm and normally does not fit any A body. Original T/A and AAR boxes were the same ratio as any steering box (15.7) with 2 changes. 1. It had shorter stops built into the box. This makes sense as the wheels turn more with the longer, specific arm. 2. The spline timing was unique, as it prevented a TA/AAR arm from being installed on any regular box. The factory never offered a longer idler, as the change in ackerman angle really isn't much of a concern in the real world.
The aftermarket fast arms have spline timing the same as any other pitman.