Tom,

In order to prevent the shock rod from spinning while trying to remove the
top nut try this:

The top of the threaded portion either has an allen opening in the top or it
becomes flat ( this will allow you to either
place an allen wrench in side the top of the rod (Bilstein) or you can use
1) use a crescent wrench- aka adjustable open end wrench to hold the
flattened top of the rod.
2) fit a boxed end wrench on the nut....I think it's a 17MM......
3) of course the boxed end wrench goes on first, followed by the crescent or
allen wrench on the very top, above  the threaded portion of the where it
becomes flat.

That's all Folks

Malibu Tony 85' Westy w/ Bilsteins and MXT's all around