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Mine has a 3/4 ton Chevy rear end in it with perches I welded myself, so it isn't going to help you much.
But the center pin (bolt) is supposed to look like this:
and just slip through the hole in the spring perch (with the nut on top slipping through the hole in the u-bolt plate).
Nothing should be bolted together, except for the leaf springs themselves.
Sounds like your only option is to remove the bolt/perch assembly from the spring pack (remember the clamps), cut the bolt, and replace it with a proper spring bolt (or at least a hex bolt with the head ground round).