You are dead on. Mine looks exactly like that including the welded end. The arm with the slide pin has broken loose from the shaft. I am pretty sure I can take the assembly off and tack weld the arm to the shaft. Car drove very strongly when this happened. Press on the pedal ant it barely responded.
When you get it back together operate the
carb linkage (engine off) full travel and verify the pin can move up into the slot. Mine goes to about the halfway point. If I understand how it's supposed to work what happens is once the
carb has gotten to full throttle you can still push the gas pedal a little more which pops the pin out of the bottom recess and it will move up into the slot. The
part of the linkage driving the
carb will not move farther but the other
part of the linkage that goes to the transmission will still move and that's what makes it downshift when you push the pedal "beyond" all the way to full throttle.