Well, since we seem to be asking for the moon how about this.
The B&O had almost 16,000 M-26 and M-27 ARA type boxcars, and these were seen all over the country. They were almost exact copies of the PRR X-29 which Atlas makes. Atlas has produced B&O ARA boxcars, but mostly post 1955 with the large B&O letters. Atlas did an ARA boxcar with the pre-1937 scheme, and one with the short lived 1945 scheme (hard to find).
So how about doing an ARA boxcar in the 1946-55 scheme (Post War 13 Great States). I have not seen this on any boxcar other than on Weaver/Atlas Wagon Tops.