Ryan,
Thanks for the question. By 1967, the Monon probably didn't have many operating passenger cars left in the stable. For sure, all of the older coach cars had already been converted to MoW (80000-series) cars, pictures of which we see frequently. We know that the business cars were all sold by then - #1, #2, #3, #90. Probably the only cars left were the ones purchased last during the Barriger era. Except for the business cars, I've never seen a photo of a former Monon passenger car on another railroad.
George L.