My dial up is not opening up the centric site
https://centricparts.centriccatalog.com/
However, several years ago I did a print screen and copied the pic to my computer
It has Caliper Kit, brake caliper repair kit, 123.133, Girling, Rear, 143.35009 (that is the centric part number)
I hope the catalog site opens up for your as it is from like 4 years ago. I have ATE brakes and the centric ATE caliper repair kits come with the O-ring that goes between the 2 halves. I don't know if the girling kit also has that but if I remember correctly you can access a picture of the kit.
Calipers are kind of assemble in the reverse of dissemble. But that requires you to note the position of heat shields if there is any and or cutouts on the pistons if there is any. The way the dust boot fits/interfaces with the heat shield on the Bendix type is different then the ATE or Girling.Some have said some of the caliper kits are not coming with new heat shields.