IMHO, the frame "variation" listed in the Greenberg book is simply a listing error, which was propagated in the Doyle book.
As far as I know, the 627 did not have any lights, the rest had a headlight on one end only.
Some models had operating couplers, others did not. I am not aware of any 44 ton engines that were known to have a operating coupler on one end, and a dummy on the other end. To the best of my knowledge, each model left the factory only one way.
It is very easy to swap operating and non-operating couplers on most switchers. Just as it is easy to swap trucks.
