You have several choices in steering boxes, and the first is whether you want power or not. If you’re modifying the Jeep enough to justify a steering conversion, you’ll want power steering. If you can get a Saginaw box from a Jeep, it will bolt up easily and won’t require a special pitman arm. The most common source for suitable Saginaw boxes, however, is GM cars. The one you want will have an input shaft with an 0.80-inch-diameter input shaft (most common on 1960s and early-1970s cars). You will also want a power-steering box with four attaching bolts, not three, for strength.