I don't think I would mess with the Walthers car. The Atlas Hart chutes are closer, and neither have the correct sides and/or end slopes.
It looks like if you took the Trainworx Quad or Atlas 90T, remove the last rib on each end, (giving you 11 like the photo) and completely rebuild the end slope, you'd at least have the right rib configuration for the side, not considering major dimensions, overall length, panel widths, etc. Then put the Hart chutes on the bottom, fabricate the bottom for the new end slope, and extend the middle support from the ends to the new slope. Still would probably be a major foobie but that would be the quickest way to get something close, I'd say.
Looked at the Walthers car again...you might be able to extend the length on it and make it work, too. It just seems like the ends are so chunky on that car that even the Atlas 90T would be better.