The shackle pins are tapered and fit in tapered holes in the side plates. Yours shown with the bolt drawing it up so tight the side plates bend might not be helping the fit at the tapered ends.
The shackles for larger trucks have nuts on the ends of the shackle pins and don't need the carriage bolt in the middle. One through two ton trucks use 2" wide front leaf springs and the smaller trucks use 1-3/4" wide springs (front and rear), so the shackles/pins and bushings aren't exactly interchangeable from the larger trucks.
Perhaps there is still a 1-3/4" wide shackle kit with the nuts on the ends of the pins, I don't know.
Picture shows both types, but these are all for 2" wide springs. Not sure why the different length side plates or which application gets which ones.
