The major problem is that the plans are of a full size engine of 1840's design. I suggest that you find plans for a simple model engine of similar looking design and then fudge to fit and paint to match it similar to the original engine. There was a model of one of the civil war monitor engines that was done, it may give you some ideas.
Gerald.
you are correct the plans are actually of the original engine and some of them are 5 feet long.
Here is the issue the complete plan is to build the entire ship which I have about 78 drawings of the ship the engine and boiler. It is a static model about 8 feet long at 1:32 scale. To build the model as historically correct as possible I have to use the original engine drawings. What is missing is all the piping and fittings from the boiler to the engine. That is a total guess.
What is lacking are isometric drawings of the complete engine front, side, top and bottom views so there is no way of knowing what the complete engine looks like.
I am starting with the engine because that is the hardest part of this build, If I can not assemble the engine the rest of the project is a mute point. Making the engine move with an air pump was an added thought and really not part of the original building plan. That is way harder than I imagined.