Secret project eh?, well I could tell you how, but then I'd have to ..............
Seriously, I dont know of anyone that has done this, but looking at the engine, there is not much of the original you would use, (only the top ends)
you would need to fabricate a new crank, new cranckcase,new induction manifold..etc if you want a compact aero engine, but as its a secret I dont really know what you are aiming at
maybe you just want to bolt two together for a laugh, who can tell?