Daniel,
To my knowledge, no one has made that Wabash car, that I know of, but that doesn't mean that it hasn't been. Most of the cars for excursions, again AFAIK are leased from historical societies, and private individuals. Result was that sometimes between excursions, the layout of the train would change, depending on leases, and such. So really you could get by with just about any cars from any pictures, as long as the car's general appearance is close enough.
Now, about the BLI. If you want to use it for a Southern excursion train, the paint scheme is completely different from the T&P colors. The loco was painted in SRR freight colors, black with graphite smoke and firebox. Don't remember what color the cab roof was. You may want to see if BLI will bring out a SRR version.