I had thought that they were integral with the dash but I was wrong.
In the 122 the padding is glued to the metal but not the 140/164.
(I have a dash panel in my garage that I plan to put into my 164 before long)

It is held on at the bottom with spring clips that have teeth that dig into
the metal. These can be removed using a thin putty knife to push the teeth
away from the metal and slide them off the edge of the pad. The pad is folded
over the edge of the metal and may crack when unfolded. There are also
spring clips at the top that go in through holes that hold the top down to
the metal. I think these will just slide out when you pull the cover off.
Note that the cover may be stuck to the dash metal.
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma