How many cars did the D&RGW field in Durango back then? If I recall they had:
8 - 330 series (330-337)
2 - snack cars (126, 212)
4 - vestibuled cars (319, 312, 323, 327)
1 - former Parlor (no "u" please) (350)
6 - open gons (400-405)
That's 21 cars. One 11 car set and one 10 car set. It seems the B-2 was a nearly-permanent addition to train 463 for years to fill the other train out to 11 also.
I did ride behind 476 one rainy day in 1968 with 11 cars and the B-3. It was a very slow trip.
Where's Woody?? He could sort this out for us.