I had given that quite some thought before I posed the query, the Trout Pass is the only "maybe", there need not have been many F&CC carloads, whatever MTY's that were available might have included one or more Gold Belt road cars in the rake.
There is also the possibility that shipments of equipment may have been supplied by the Florence foundries such as gate valves etc. The Oil industry supply was big there but I'm only guessing here since Denver had a massive number of foundry companies.
The Cement shipments, a rather roundabout routing but no cross gauge transfer, would still be foremost in my mind.
UpSideDownC
in New Zealand