The DLC isn’t complete yet, and it’s being made on the spare time of those who contribute their mods to the DLC.
Little or no information may be available for trains that early, that fit the scenario of being used in the Nordic countries, thus there’s only one choice right now. This will hopefully change in the future. When? I don’t know. I’m not the one making the steam engines.
I understand it’s frustrating, but at the same time; one mod take tens of hours to make. Those who make the mods will obviously make whatever they feel like doing, with whatever information they have access to.