It seems like going with a 56cm and raising the post would help get you far enough behind the BB but then you might run into issues with seat drop, which it sounds like you do.

Bob Jackson would be the first place I would look for a lugged steel frame. I dont think their custom prices are outrageous either. Rivendell might be a place to look as I am speculating that they like to throw together a fairly upright bike, also if you use a threaded headset with a long nitto quill you might be able to achieve the position you are looking for.