That's the kickdown/transmission pressure rod and throttle cable hold down. It mounts to the manifold.
The slotted rod does connect to the carb and there should also be a spring that hold the rod forward. If you're using a Holley, there's an additional piece that can be purchased to adapt it and it mounts to the throttle itself.
Never run a 727 without it (with the exception of some modified transmisions).