The build notes that Hemmingway supply along with the drawings are basically a reprint of the article but a bit pricy compared to a couple of scanned pages.
There is also a 4 part article starting in 4180 of 2002 vintage on building the engine which just comes into the digital archive. I don’t have Vol127.
Looking at the drawing I would be interesting to work out the cost of raw materials compared to buying castings as it could all be made from bar stock with the cylinders being the only items that would need some creative carving out from block if you wanted to stick with a similar outside appearance to castings, a lot easier if you alter the shape to make machining easier.