Transition sleepers are superliner IIs.
Some El Capitan step down cars were used as crew lounges and served the function.
There are baggage cars of many lineages that are plausible. The Atlas CZ car, deskirted is a possible option for a baggage car up to a point. The later baggage cars with the rollup doors are converted ex ATSF cars. I suspect you'd have to build one of those.
