1981 was the first year of the new D&S. Prior to this in D&RGW days they never ran 2 K-28's doubleheader across the High Bridge, as there was a weight restriction. They did however run with a 3 car split on some trains....see link below to a trip my dad shot.
When Bradshaw bought the railroad, he upgraded the line, including strengthen the bridges, so they could run doubleheaders, and the bigger K-36, and K-37 497 across. We were there at the end of June, and early July, and they had not strengthened the bridges yet. I guess by your trip the work had been completed.
Quick shot in this preview of two engines split by freight cars in 1961. This was a fall foliage trip, that started with 483 in Alamosa (3 day trip).
Greg