M thinks I would try to offset the crankshafts by 1/2 the noumber of degrees between cylinder firings. Lets see, cylinder fires once in 720 deg, div by 8 cylinders, thats every 90 degrees. So, offsetTDC on 1st engine (compression stroke) 45 deg. from same position on 2nd engine. Now have power pulse every 45 deg, vs 90 deg in V8. Run lot smoother. As to coupling - just use universal, perhaps constant speed type? Engines need to be mounted to "float" a little bit, yet Ujoint keep timed. NO?