Some pictures on Dennis Taylors 80's Rail site
http://80srail.zenfolio.com/p904823333
Well done Brian it looks like an emergency screw coupling to me as well. On some of the NXAs that were branded for Motorail use some of them had drop head buckeyes fitted, but that does not explain the use of the emergency screw coupling. It could have been something in the appendices for the use of these vehicles?
In the above set of photos the one showing E96291E coupled to another N/C car carrier with the doors open (the one that you can't see the number of is E96299E) you can see that its got two sets of roof lights in it. When you look at it it does look like the roof lights are not off set from one another. That would explain why at one end one is closer to the end than on the other side, so that is about the only way you could tell one side from the other.
In the next photo showing E96299E at the unloading ramp wagon you can see the roof light very well on the R/H side of the vehicle but not so clear on the L/H side. You can just about make them out.
So if your worried about the time frame! I'd be more worried about the details in the kit (not that any kits have any mistakes in them). Or could there have been four different type of roof in such a small number of vehicles? No roof lights, roof lights down the centre, roof lights on one side and roof lights down both sides.
I know what I'd go for, I'd be getting the saw out, or just put a surround on the roof and covering them with paint and muck to look like roof lights.
OzzyO.
PS. how many of them were built? for both the wagon fleet and the passenger fleet.