David (Rocky Mountaineer), thanks very much for your comments. (I've been out a few days and didn't get a chance to respond earlier.) You were one of the few who seemed to understand what I was originally asking, although I certainly didn't think it was all that complicated! 
Your comments and photos are certainly the most helpful and definitive. It seems the conclusion would be that while the 2008 GS-4 might be an identical match for the aluminum cars, the 2016 GS-4s are very close, close enough that it is probably not a discertainable difference or enough of a difference to matter to most people.
One other appearance issue was raised by your photos, however, that being the alignment of the striping between the engine and the tender. Their relative placement on the shelf surface may well be a factor, but it does appear in the photos that they are somewhat out of alignment.
