The first thing you need is a seal kit. The only place in the known universe to get a complete kit is from:

John A. Vargus
P.O. Box 201195
Austin, Texas 78720

Before you contact John you need to know which box you're rebuilding. Study this picture... The box on the left is from 86 & 87 while the box on the right was used from 88 through 95. There are a few distinguishing characteristics. The casting for the 86-87 box is smoother looking overall with fewer bumps and lumps and it has a lock ring around the steering input shaft. The bolt-on casting that supports the input shaft also protrudes about an inch less than the one on the later box but in all other aspects they are functionally identical. The input shaft and sector shaft have identical dimensions and spline counts so both boxes can use the same pitman arm and, if there is enough slip to accommodate the different lengths, steering shafts. The mounting flanges are also identical so either box will bolt-up in place of the other.

 This is the '86-'87 steering box pulled apart. The end caps take a little persuasion with a brass drift but the shafts pulled out with very little persuasion in spite of the box being 15 years old.

The casting is on the far right, below that is the sector shaft and it's cap. In the upper left is a box with the recirculating balls. Below that is the input shaft and piston, and below them is the cap for the input shaft. This cap has fittings for the power steering inlet and outlet hoses.

 I decided to start with the seals for the sector shaft near the pitman arm. First I cleaned up the inside of the casting with Scotchbrite so the seal would slide in easily.
 In a routine I also used while replacing the rest of the seals, I layed out the old seals in the order they came off the shaft/out of the casting, then set out the new components in the same order. Here is the o-ring, Teflon ring, metal collar, snap ring and seal for the sector shaft just above the pitman arm.
 The Teflon ring fits inside the o-ring ring so the teflon will contact the sector shaft.

You like that bruise under my thumb nail? That happened when my BFH went feral and attacked my thumb while I was replacing a shackle bushing a couple of weeks ago.

 After putting in the metal collar and retaining snap ring, the seal is driven in. A seal driver with a broad assortment of driving pucks makes it easier and less stressful.
 The upper end of the sector shaft is supported by this cap and roller bearing. A single o-ring goes in a groove on the outside of the cap where is slides into the main casting.
 In order to replace the sector shaft cap on the main casting, this adjustment screw must be backed out pulling the cap on in the process. The adjustment is rumored to tighten up play in the steering box, but I couldn't detect any affect through it's range of adjustment.
 Next up was replacing the seal on the piston. An o-ring inside of a Teflon ring goes in the channel at the top of the piston.
 When placing the piston in the main casting be very careful about 2/3 of the way to the bottom. There is a sharp lip that will cut the Teflon ring if it is not pressed down and eased past the sharp area. Don't ask me how I know this. It was a good thing I had two seal kits, even if one was for the '88-'95 IFS boxes. The piston seals, thankfully, were the same size in both kits.
 The steering input shaft has 2 Teflon rings -without- the inner o-rings.
 The cap contains a roller bearing race, which needs to be reused since the seal kit doesn't contain another one, an o-ring, and an o-ring/Teflon ring combo.
 When the seals are replaced on the shaft and in the cap, the shaft is inserted into the cap. In this process I damaged one of the Teflon ringss, and this time they weren't the same size as the ones in the other kit. I ended up using the better of the two old Teflon rings. You really have to finesse the Teflon rings on the shaft past the outer o-ring in the cap to prevent damaging either.
A crucial step I -don't- show is the replacement of the recirculating balls. I was so focused on figuring out how to reinstall them that I neglected to take a picture. I should have the opportunity to take pics when John does his next weekend. This is the drill: Inside the piston is a spiral race that matches the spiral race on the steering input shaft. There is a tube that interrupts the spiral race in the piston near the top and bottom providing a continuous path for the balls to re circulate. It's sort of like slides and ladders with the spiral race playing the part of the slide and the tube playing the part of the ladder. First fill the tube with balls, then pack the entirety of the spiral race between the inlet and outlet of the tube with the remaining balls. I did it with the piston on its side and the spiral race coated with a thick layer of grease to hold the balls in place. I used a small flat bladed screwdriver to pick up a small blob of grease and a ball then plaster it into position in the spiral race. Once all the balls are installed, carefully thread the spiral race section of the shaft into the spiral race section of the piston which now contains all the balls embedded in a layer of grease.

A second step I didn't get a picture of is driving the seal into and installing the adjustable race for the top of the steering shaft. This adjustable race isn't present on the '88-'95 boxes. Once the seal is driven in you use a pin spanner (I used a Park Tools pin spanner I had for a bicycle bottom bracket) to set the preload on the bearings then lock it down with the lock ring. I used a brass drift, but come to think of it I could have used my bottom bracket lock ring tool.

There was a small scare when I had the box re-installed and it shot ATF out the top like Old Faithful with internal bleeding. A classic long-day blunder, I hadn't fully tightened the lock nut on the adjusting screw... Today I drove around town, going lock to lock at every opportunity, and the box is still clean and dry. Tighter than an aquatic mammals's sphincter, baby!

 It was steering box day in my driveway with me rebuilding mine and David beginning his crossover steering swap. I think we spent most of the day, when not cursing that something wasn't going right, looking at one another and secretly saying to ourselves "at least I'm not as dirty as -that- looser!"