Hello,
I had another post about the removal of the rear calipers from the IRS, I decided to start a new post for the re-install as for my model it seems there are some confusing bits of how to do this. Having rebuilt the calipers and other parts of the IRS, I have already forgotten what goes where. And with the differential sitting on the floor, sometimes it is confusing which end is up. So with the Diff sitting with top side up and the connection of the drive shaft showing forward, now I can proceed. To install the caliper you need to knw which one goes where , Right and left, in my case Passenger side (RT) and Drivers side (LT). I had tagged them, but after painting and rebuilding the tags were gone!
In my case I have the caliper and a bracket which attaches to the caliper using two bolts, lock washer, a spacer and a shim. See other post for how dirty and rusty looking these parts were. I will post the caliper rebuild.

See items 11, 12 and 13

Differential with disc on RT side. LT side will be where the caliper and disc are installed

Since here is the bracket, spacer, shims, and bolts in the right position. Shims help to center the caliper with the disc

The shims + spacer fit unto the caliper with the bracket

two holes on this bracket to install bolts, before mounting caliper, otherwise non-accessible.



How to access the bolt once you put the disc and caliper in place. The hole access moves to 3 positions as you rotate the differential as in the next photos



Caliper and disc first bolt

 

Nice looking job. Very clean and tidy.
I found the best way to determine the side the caliper goes is to make sure the bleed nipple is on the top. If you put the calliper on the wrong side the it would be upside down and the bleed nipple on the bottom.
On the subject of bleeding have you considered putting a bleed extension in place. Bleeding the brakes when the IRS is in position is really difficult so a friend of mine has fitted extenders from the bleed nipple into the boot of the car so he no longer needs to struggle under the car anymore. They are a pair of braided brake lines from the bleed nipples through holes in the boot floor with the bleed nipple on the ends.
In the 1970s garages working on the XJ6 used to cut an inspection hatch in the boot floor just above the IRS cage which allowed access to the bleed nipples and pads on the hand brake. The hatch was hidden under the carpet and held down with self tapping screws but apparently it made the work on the rear brakes so much easier. Not done this with my S Type but then again I have not had need to get to the rear brakes and with the mileage I do not likely to have to get there in the near future.

 

Very good observation about the bleed valve, and I would add the brake line connections. I was in the process of putting the caliper on the wrong side, and was puzzled about which way the bracket was supposed to be positioned. Many of the videos have a similar caliper, but not the same as my 420, and they require a centering with respect to the disc. These too have to be centered, hence the shims where already installed initially. To get myself oriented, I returned to the photo taken before removing anything from the car.
In the photo you can see how the brake lines run, and where they connect. From there I could begin to figure it out.

I am not sure based on this photo if I will have a problem to bleed the brakes with out making an extension. Seems like I can reach it as it is from under the car.



The before photo of both calipers