Hi, Can someone tell me if I really need to change the actual gearbox linkage arm coming up from behind the inner casing, that the longer connector rod which goes to the forward controls, fits to.  

I did'nt,can't see why you would..

WAZ..

you either have to remove the shaft, (pull primary apart), cut the shaft off (from in behinfd the primary) or leave it there and secure the std linkage somehow (this is what I did & made a hidden bracket to secure it)
I also machined a cover for the spline that the original shifter clamped to.