Yes, the single carriage bolt is there. I got the shackles from Jim Carter. They're listed as for a 55-59. They installed without any trouble. It's just that the pin that attaches to the frame and the one that goes through the leaf spring are threaded and you have a nut on the ends. Seems to me that if you tighten them, they can't pivot, but that would be the case with the carriage bolt as well, so that theory doesn't hold water, I guess. They're 3/4 inch nuts, so I assume you tighten them pretty securely. What's not clear to me is how they can move if they're clamped down with nuts on either end.
