OK the shackle, the actual place the bolt goes through is supposed to swing towards the spring if this does not move at all it is seized and needs to be freed up, try loosening the next bolt up to be able to swing it towards the spring. These are usually set to 65-87 ft.lbs. of torque. So not all that tight. The bolt has seized inside the shackle itself most likely by loosening it will allow it so swing forwards to attach it. once attached torque it to the given amount and be done.
last year I replaced my springs and anti-seized the bolts to try to prevent this issue. They also make bolts that have zerk fittings so they can be greased to prevent squeaks and seizing.