To a serious engine builder, a "stock" engine is just like an artist's blank canvas- - - - -boring, but just the thing upon which to make a masterpiece. Engine parts don't know, or care which manufacturer's equipment they are supposed to fit. Any real engine builder with a little creativity and access to some machine tools can make those parts do things they were never intended to do, and work in places they were never intended to go. The guys who get obsessive-compulsive about "XXXX" part number being the only thing a particular engine can run probably need to get a life- - - -or maybe a girlfriend!
LOL!
Jerry