depends how much u want to spend and what u want out of it? if you simply just want to lower ride height you can get away with a set of lowered king springs to suit your 33. if your after a smoother ride and lower height i'd go a good set of new coilovers, that way you can adjust up and down etc.
if you were to just do springs i would def think about putting some new shocks in as 15yr old shocks would be knackered by now.