Since you plan on replacing ubolts and possibly shackles and the springs. Remember if it does not come loose you can always cut the ubolts. Lots of shops just do that out the gate for speed. But remember lots of safety when doing that. After a few days of soaking them good. I just put a socket on with a long breaker bar got the loose rocking back and forth then zipped them off with 1/2 inch battery impact. same with the rear spring mount bolt remember there is a nut on the backside AND its threaded on the inside. Take nut off first. Also I would go with this style shackles up front gm switched to them in 57 for a reason. They work on 55-59 models as well as the older style on the 55-56 models. So you will see both kinds listed for all years on most sites. I found my older style with just the center bolt actually got bent by the bushing shaft self threading itself to one side.
