Hi Dennis, thanks for your reply.
I was not aware of the tank bottoms being white, the ends of the rear cross members makes sense for black out, on the subject of black out markings it apeers my rear dif was never painted white as there is no evidence of white paint on it.
The thing is the entire truck looks to have been painted white, there is white showing through on the entire rear cross member, doors, bonnet, windscreen frame, tail gate, bulk head and seat box. The tub was not included in the sale so I can't say if it has the layer of white or not.
At first I thought nothing of it as it looked as though it may have been painted white post retirement from the Army, but when sanding back the layers it's the second layer after the first coat of Deep Bronze Green.
I don't have a good photo of the stiffner plate but you can see the edges of it in some of the photos of the white on the rear cross member, I'll post a better photo of it later.