4.0 main bearing bolt size question

Hi all

I am trying to change the rear main seal in my 1997 4.0 Jeep Grand
Cherokee. I have been pretty much over my head in the whole project.

In trying to remove the main cap, my 13/16 socket seems too big, and my
20mm socket won't fit on the main bearing bolt.

Does anyone know what size these are? At first, I thought the 20mm
socket just needed to be deeper so I just got back from the store with
a deep socket and it doesn't fit on either.

I do not have a factory manual.

Thanks in advance.
Doug