340 exhaust manifold

hey guys just going through all the parts piled in my 66 signet. i found an extra set of manifolds, any one know what part number 4006741 is off of? i tried to do a part number search with no luck. it looks alot like a 273 manifold but doesnt make the hart turn at the flange. maybee 67 &later a body 273? or 340?