A rather similar double Tangye steam engine, which can be built as a single, was written up in Model Engineer by Edgar T Westbury, in a series from January 1954. This was based on a Double Tangye engine buit by another model engineer and written up in ME mag back in 1933 ! By chance I do happen to have the issue from that early date, with the GA, - it's essentially just the same as the 1954 GA partly shown in my photo - and the photo atop the 1954 article is of the 1933 engine. I've got the mags with the 1954 article series here, but though I had been hopeful that they would be the key to your drawing problem, the engine doesn't seem to be exactly the same.
The photos give a sample of size and layout of the Westbury Tangye, you may be able to tell whether any further details would be helpful. My feeling might be that, with some idea of the detailing and configuration of this ME version of the engine, it could be easier to suss out an appropriate design and dimension schedule working with the castings that you have, rather than be chasing after very elusive drawings? Unless someone helpful does announce that they have a set of them stuffed in a workshop drawer ... Dave
