I need to remove the fan and viscous coupling from in front of the water pump pully. What size is the nut on the end of the pully shaft? Looks like 1 3/8. Thanks

 

Looking at the catalog from Atlantic British, the speciality wrench for a D1 up thru 95 is a 32mm and it is very thin so as to be able to slip in to reach the nut. They don't show a wrench for a newer Disco so I don't know if there is a different on or not for yours.
Mike

 

Turns out to be a 36mm. I forgot some vital info. on my post-'96 Disco 1. With some effort and a few scars I got the viscous coupling off the water pump pully.