Alco K's

I seem to recall from way back when, that both Baldwin and Alco bids were considered for the 470 class engines. It may have been a "package" that included a Standard Gauge project as well.
The 470's incorporated several "improvements" over the older Mudhens. Among these were the smokebox mounted airpumps, which were placed there at the D&RGW's request to improve visibility from the Fireman's side. Another interesting change that was quickly corrected, was that the water feed pipes to the injectors were located at the rear corners of the tenders rather than the front corners. This was done to be able to pull water from the entire tank on heavy grades. There were problems with the pipes tending to freeze in Winter conditions, and the water feeds were relocated.
My understanding is that the K-28 type locomotives built for the Oahu all had side mounted airpumps, and kept the rear tender feed pipes till the end.
Another obvious difference was the single visible counterweight on the main driver, which was apparently to counterweight the valve gear and main rods. The siderod counterweights were all located on the wheels, invisible from view, which presents a much different look than any of the Baldwin built K's.
Another, of course, is the rounded corners of the cabs, which may have been typical Alco at the time.
Finally, the K-28's also came with the modern looking coal bunker side sheets. This was a first for "new" Narrow Gauge engines on the D&RGW.
It might also be an interesting question why the D&RGW returned to Baldwin for the 480's. There certainly can't be any question that the Alco-built 470's were successful in every way imaginable.