And in the two engine vein, the deHavilland Buffalo looks way more like a
Herc than a Dash-7 does. However, none of these match the original
poster's mention of "proposed to build the production aircraft in
Puerto Rico"

I assumed this plane was powered by turboprops, hence the -7 mention.
Now I'm hooked - gonna have to dig up my old Jane's books to try and
figger this one out...