OK, I'll go with a plain steel floor. Many 65ft gons had them, so it wouldn't be surprising.
I'm trying to kitbash something similar from ConCor parts, which need a new floor, as the CC cars are too narrow. Evergreen 0.030 spaced siding works beautifully, as far as measuring (3.90 inches long matches the BLMA/Bluford cars), but if it has plain steel flooring, I'll put the scribed side down.
Now all I need is to find an appropriate end. I have a few options in scrap cars, but will have to see what fits best.
Thank you!