You can get an Athearn MofW Gondola for $5-6. They come marked in a tuscan red "wheel loading only" scheme. The B&O really set itself apart for MofW equipment with their "devil red" scheme. If you want to paint an undecorated one red and decal it, you would have a much better model than mine.
Below is a pic of a real B&O MofW
Dean Heacock pic.
The Athearn kit is very simple to assemble. The interior comes the same color as the outside, so it will need to be painted. The insides rust quickly and seem to be black in color. Also there are no consolidated stencil decals or ACI cards on the original kit. I added mine to this kit.
Also notice that the ends of wheel loading cars are cut down with a red bar along the top. The Athearn kit has solid ends, if you want to cut them down, that would make them more prototypical. Out of the box this is barely an 80% sort of kit. Unfortunately, there just isn't that much on the market when it comes to gondolas.
Below is a pic of my Athearn MofW gondola.