manual steering boxes

All of the A-body manual boxes are "small" sector & interchange.

If you use a B-body/Truck/Van manual steering box that has a "large" sector...then you will need a 73 & up power steering pitman arm for an A-body. But don't use a "B" body manual box if you have headers.

A large sector box will bolt up & work just fine but the top of the box is built different. Most headers won't clear the box on the top by about 3/8" & on the bottom by a 1/4".