If you plan on doing them yourself- Here is what I do to most of my customer
springs. They are 
usually weak and the rear of the car is sagging. The following will return your
ride height- without 
sacrificing ride quality.
        1) Remove the springs and disassemble- including pressing out the
bushings. Mark each spring for 
reassembly- I usually mark in a place that is hidden when assembled.
        2) Wire brush (on a grinder) the springs and POR-15 them
        3) Purchase new spring seperator material if the old is deteriorated
        4) find/purchase a used set of (matching size) springs (I have bunches
of extras)
        5) Remove the main leaf and 3rd leaf from the used set- clean/paint as
above
        6) Cut the main leaf's spring-eyes off about 3" from the eye, cut 3"
from each end of the 3rd 
spring. This will make them fit better when added to the original springs.
        7) Purchase new through-bolts, 1" longer U-bolts for the rear axle, and
some new spring-clamps.
        8) Assemble springs- by length- including the 2 extra springs each
side.
        9) INSTALL- and drive the car around.
        10). IF the ride height is too high, you can use a die grinder w/cutoff
wheel- to remove sections 
of the 2 extra springs- about 3" at a time- until you reach a height you like.
Be sure to drive 
around a bit to settle the springs at the new height. Typically, removing metal
from the rear of the 
spring- is more effective in lowering the car.

Ray   Fikthorn  Dec 2003