I'd say that is correct. You do need something for sure. I dont believe there is enough adjustment to get right as it shown.
Just a dab of FYI...
the earlier models didn't have that slot. If something interfeared with the kickdown linkage it could and did hold the throttle open. Some of those had the bellcrank mounted to the firewall also. just a broken motor support would create a runaway car.
That slot allows the throttle to return freely, regardless of kickdown linkage conflict.
Once properly adjusted the back of the slot will rest against the throttle pin at any throttle position.