I just had a closer look at that photo, and its not a GS. Front exhaust and the top of the guards looks like its also an FFW, or at least a radio vehicle.
The FFW I had used brackets behind the seats for carrying the gardening tools, and the aerial tuner mounted on top of the guard.
If you look at the top of the guard, towards the rear, there is a square hole where the armoured cover carrying the aerial cable came out from under the guard. The are 2 other holes in front of it where the aerial plug screwed into a holder.
Definately an ex radio bus