I believe the swaps (at least the initial ones when the steel cars were first built) were documented in one of the very early Colorado Railroad Annuals. I bought the single issues from the early 1960's when I first visited Durango on the Illini's 1966 "Journey to Yesterday" trip. I also have the multiple, bound volume but they are all at home. Older passenger equipment that was in M-of-W service "donated" their passenger trucks. I'll see if I can post the information this evening as it was documented in the early days.
Don C.