"Kickdown" rod for 727 BB

Kickdown linkage is generally what the whole setup is called. Also Torqueflite "throttle linkage"
Details varied over the years; most common are the later 60s and into 70s three piece linkages with two bellcranks. That was followed by the "one-piece" kickdown linkages.
Some illustrations in here:
Shift Quality & Linkage Adjustment (Session 279) from the Master Technician's Service Conference

Some are now available as repops. For just the intermediate rod (sounds like your situation) try some transmission shops and people parting out cars, etc.