Manual valve body.. do you need a kickdown linkage?

Completely depends on the valve body. As above, if it is a factory vb modified with a transgo tf3 kit into a manual vb it absolutely needs the linkage, or at a minimum to wire the throttle valve lever on the transmission wide open which will make it not street friendly. If it is an aftermarket vb it likely does not need the linkage, but I would recommend that you contact the vb manufacturer first to know for sure.