It would be quite a step from what you have made to lady S. being a small engine with a lot of detail many of the parts are quite small as are the fixings.
I would be tempted to see if you can pick up the old issues of EiM from ebay or similar to see what is involved and the build article will be a lot of help too.
These days with many of us having milling machines it may be better to cut some of the items from solid rather than use castings just picking the more difficult to make ones like the beam and flywheel.
If it were me I’d make from scratch at a larger size and pick a few details from some of the other coffer based six column engines images of which can be found on the net.