Be aware that the sector shaft diameter changed (increased) in 73. That means that you need to get the correct pitman arm for your steering box.
Also, you'll probably need a steering shaft adapter since the steering shaft for a power steering box is shorter than for a manual box. Flaming River sells that adapter.
Something else that I found out was that that pre-73 A-body pitman arms connect to the bottom of the center link and 73-on pitman arms connect to the top of the center link.
Hope this helps.