powerglide vaccum modulator
Pretty sure the 64 unit has a vacuum modulator...it is needed for the upshift and downshift in normal driving. The kickdown linkage is used to manually downshift for passing and is adjustable and works with the throttle linkage when you floor the gas pedal.
All vacuum modulators connect to intake manifold vacuum...there is typically a fitting in the intake manifold for the connection. Most have a short rubber hose at each end of a steel tube which is bent to fit the application...some vehicles will have a manifold fitting that has two connections, one for the modulator another for the power brakes if equipped.