Valve train geometry

Then why are the 'Cranes' wrong on any head you put them on!
The rockers aren't wrong for the head, the head is wrong for the rockers. The mounting points are in the wrong place. The rocker is nothing but a fulcrum, and I can make just about any rocker work on any head as long as there is enough room under the valve cover to fit it. It may not be an efficient rocker design for that application, but it will open and close the valve.