The sector shaft connects to the pitman arm. There are two sizes which are grouped into "large" and "small". Most factory manual boxes are small sector with exceptions such a C-bodies and Vans. Power steering up to 72 was small sector, 73 and later was large sector.
If you have a small sector now and the steering box turns out to be large sector, then that could be a problem depending on the year of the car. You can't easily use a 73 and up power steering pitman arm on a pre-73 because Mopar changed the orientation of the ball joint end. Early ones had the threads pointing up, later ones had the threads pointing down.