Working this now on my FJ40 w/ 400 SBC. I could not access a spark plug w/out pulling the steering box. Since my center arm needed rebuilding, I went ahead and got parts to rebuild it, the drag link, new seals for the box and new rag joint.
I suspected the steering box being close to the manifold (1/2" space) the inside would be baked. This was not the case. The inside was in perfect shape. I had a bad seal on the pittman arm shaft where lube poured from and made a huge mess over time. As others suggest, look at a power steering conversion to delete the box. I will go that route eventually but have too many other things I am doing on my FJ for a major project like that. I'll post some photos this evening.