The freight cars at Knott's came much later after the passenger train. I think it was after the D&RG discontinued Durango to Alamosa when the cars were being sold off.
The stock cars were modified by cutting the side sill and installing steps for passenger boarding.
Yes, the gondola that remained at Knott's was rebuilt to a stock car and the stock car became a gondola. Both of these are setup with bench seating. The Knott's built stock car is equipped with a wheelchair lift similar to the kind used on over-the-highway buses. The cars retained their original numbers. These are regularly used with the passenger cars behind the steam engines.
The rebuilding of the two freight cars was reported here when it occured.
Brian Norden