hi adrian,
there is no construction series by don young for the GCR ROD loco. however it shares lots of common parts with his Immingham and Jersey Lily designs. there is a detailed construction series for Jersey Lily in ME from about 1970/1971 onwards.
there is a huge problem with Jersey Lily with the eccentrics on the main driving wheel axle – the firebox throatplate is too far forward, and in order to get sufficient eccentric throw and enough room for the eccentrics and straps don shows the eccentrics 'cut into' the axle, and the axle with eccentrics has to be turned from solid. i believe Immingham has the same fault.
i dont know whether the GCR ROD design by don has the same fault.
cheers,
julian