The Adwest Marles Variamatic steering box featured in the above vehicles was also used extensively in Landrovers, including Defenders.
there is about half a dozen Youtubes that feature all aspects of overhaul, changing seals etc
I would recommend watch them all if you have to do an overhaul
to the best of my knowledge, the seal kit is the universal for Jag and Landrover
these two cover most aspects