This end of the brace connects to the throttle quadrant. The throttle quadrants, having been reinforced with aluminum brackets (Picture 533), will provide a very sturdy mount.
Jerry made an aluminum insert to fit inside the square tube, and then staked* it in place. The insert is threaded in the center. The mounting hole on the throttle quadrant was located by setting the brace in place, then measuring from the outside edge of the tube.
*From an article titled Assembly Presses: Crimping, Staking, Swaging, Clinching: In staking, downward pressure is applied to the end of a post or shaft, creating a head, forming one or more retaining points. Bearings are often staked to shafts to supplement the interference fit, and the ends of bolts are sometimes staked to prevent them from loosening.