MTH’s interiors are pretty bland and coach interiors back then were pretty colorful. I did the same to my UP set a year or two back. This is the observation car with the curved rear. I found some pix of Santa Fe coaches and some had a Indian upholstery theme. I found some pix of designs online and sized them to fit the seats. I printed them in Papillio ink jet vinyl. Peel off the backing and stick them on. Figures are those 1/32 figures you find on ebay from China. Lousy paint job, but from the outside they look fine. 3 cars to go! Good winter project.
