Jim

Unfortunately there is no single ladder -- I have photos that
show 6 and 7 rung ladders on the sides, and 5, 6, and 7 rung
ladders on the ends. They all appear to be the same width but
the rung spacing differs.

The original cars appear to have 7 rung ladders on the sides and
7 rung ladders on the ends -- that's probably the configuration
most modelers want. The 8th and 9th "rungs" above the 7th on the
sides appear to be grabirons.

I don't think there is a commercial ladder with the correct rung
spacing so the best solution (IMO) is a set of etched brass ladders.
Unless someone can suggest commercial 8-rung or 9-rung ladders which
approximate the rung spacing of the B&O ladders.

I don't think you would need to make "dimples". The standoff posts
(or whatever they're called) may have different locations for different
ladders.

Tim O'Connor