What steering box do I need?

If your power box or K frame has not been changed to the 73 and newer style you will have a small selector power box and it will use the same pitman arm as any A, B, and E body manual box. I believe C body power/manual boxes are all Large selector. In 73 they went to large selector in all power boxes.

If you verify the box you have works, you might look into having it rebuilt. Also consider a ratio change, as that 24:1 is a real drag on the street. Unless your going big block, you might consider having a stage 3 Firm Feel box. I just ditched my manual steering in favor of one, but my car is street only.