Your motor has the old style stamped gears, #’s 8 and 16, which can be bent or worn. Twisting the throttle with the tiller in the up position can damage them. If they are damaged, ’56 and later cast style gears and shafts will drop right in. As mentioned, gears 21 and 23 can be one tooth out of time which will prevent the mag from advancing fully Your vertical throttle shaft, #28, doesn’t have a plastic pin to break at the bottom but instead it is cast and has an ant rattle spring.
For the mag and carb to be that much retarded, I’d suspect the gear timing first.
