Why do you think you need new springs?
The rear springs tend to not be bad and may not need to be replaced. The fronts are more commonly weak. I would not replace them until I was sure they are out of spec.
With fronts, some after market springs are missing a taper at the front and rear top edges to allow them to fully seat in the front cross member. Do not forget to put in a section of frame webbing at the top of the spring.
Taking them apart, cleaning them up and lubing them with slip plate does wonders.
Once you have good working springs then shocks will be critical to safely drive over 25 MPH.
The front and rear U bolt nuts are special. Do not try to chase the threads with a tap, do not put hardware store or reproduction nuts. They are VERY hard as in a file will not hardly scratch them. The threads are also closer tolerance then your tap and die set so you will only break the tap in the nuts and mess up the threads on the U bolts. The front U bolts may have bad threads. Look close at them and do not try to fix them. They are cheap and common to find good originals.
