The idler arm bolt uses a stop nut, no cotter pin on all but one year only 67’s which had a mono connection like a tie rod end.
I don't seem to have 2 things. The first is the 2 bolts that attach the steering knuckle( I would call it a stub axle) to the knuckle arm. I seem to have a quantity of these bolt/nuts.
I’m not sure what you are saying. Are you describing attaching the lower ball joint to hub? The disk brake lower ball joint uses a larger diameter attachment bolt than a drum brake ball joint hub. Depending on year of your car, and the donor car you may have a wheel bolt pattern miss match to rear axle.