Manual steering boxes are almost always small sector. I think there might have been some large sector manual boxes used in C body or vans but I can't say I've ever seen one.
You don't need "rare parts" for that car. Off the shelf Moog parts that you buy from Summit or NAPA should work just fine.
Not when it comes to the big block pitman arm, trust me, I found out the hard way. Some applications list them as fitting but the sector shaft splines are "clocked" differently on the BB arms. It causes the center link to no longer be centered to the oil pan. In addition One has to screw the R tie rod ends all the way in and the left ones out to get the steering box centered
