I'll use an Exactrail car and think hateful thoughts as I cut into it!!! Take that you imposter!!!
Hmmm ... I would use the BLMA car instead. Look at the original roof of the Alcoa car, and the BLMA model:
The prototype's roof sits on top of the sides and ends rather than flush inside the sides/ends. The existing BLMA roof simply could be popped out and saved for future projects, and a new roof could be fabricated from styrene or etched from brass and attached without worrying about hiding the seams. MTL or BLMA roof hatches could sit on collars hole-punched from .015" styrene sheet. The five feet or so of end roofwalks can be cut from the BLMA roofwalk, or something from Plano or GMM could be used. And since the car has to be stripped/repainted - if you really wanted to get ambitious ... other than the two outer ribs, the existing ribs are too narrow and could be removed and replaced with Evergreen styrene strips of the proper width. They appear to be welded with no flanges on either side, which makes it very easy. And for the beltrail at the top of the sides, I would use Plastruct .010"x.010" strips if the Evergreen .020"x.015" is too thick.
Alclad II aluminum or Testors Model Master Metalizer aluminum provides the proper metallic finish, although I would paint the black "patch-outs" first and mask them off so as to not damage the aluminum finish. They both offer aged aluminums also. Or, you could just go with a light gray paint if the model is going to be weathered as heavily as the photo above. Decals might be an issue, but I would not let that deter the project.
Definitely doable, and the construction probably is an evening-or-two project once you have all the parts.
