I own CB750E-1007419 that is essentially a complete NOS engine. #28 Carbs, smooth oil filter cup, etc. Was absolutely astounded to find it a couple of years ago.
It is essentially all "Sandcast" parts in diecast cases. The bike was purchased specifically for the engine to be used in a dirt track cart. The engine was removed and stored. It was never installed in the cart and appears to have only been run during the dealer setup.