[dsraven]

you could also replace the stock leafs with some newer style ones that have rubber bushings for a smoother quieter ride. maybe the ones that come attached to the donor axle even. replace the frame mounting brackets with some new ones, say from a ranger or something. dorman sells lots of that stuff for a decent price. your donor axle can be located on the springs using trailer axle spring pads like lots of others use. above or below the springs. shackles can all be replaced using newer style parts from a stock vehicle that would be availabe from a local parts store anywhere you happen to be if doing a road trip some time. another thing to think about actually. availability of replacement parts in the future if on the side of the road sunday afternoon in small town noplace. take lots of pics as you dismantle, keep like parts together, boxed and labelled, keep a log of the new parts you use so you know the part numbers and what they fit.
anyway, a plan is what you need to start and then stick to it so you don't end up with a waaay bigger bill than you thought. upgrading "cause you have it apart anyway" is a slippery slope. it costs, plus it extends the build time. that has caused many builds to sit dormant or be sold unfinished. sometimes it is better to think small and get it on the road, then upgrade later as a weekend job or something done over the winter. it never fails, you get in deep and then a home project interrupts and once they get on the back burner a build can be hard to get restarted.